America's goal of stopping nuclear non-proliferation has suffered two serious setbacks in recent years. Both North Korea and Iran appear to be pursuing ambitious nuclear weapons programs. What U.S. officials have not recognized is that such actions are a logical, perhaps even inevitable, response to the foreign policy the United States has pursued since the end of the Cold War. Washington may have tried to shape the international system with the best of motives, believing that taking action against unsavory states would both enhance America's security and advance the goals of peace and justice in the world. But as generations of realist scholars have shown, other nations may not concede that the motives of an activist power are benign. What might seem to U.S. policymakers justifiable, even noble, behavior may seem threatening to nations that have a less than cordial relationship with the United States.

Consider the extent of U.S. military action since the opening of the Berlin Wall. The United States has engaged in nine major military operations during that period. Moreover, in his 2002 State of the Union address, President Bush explicitly linked both North Korea and Iran to Iraq (a country with which the United States was clearly headed to war) in an "axis of evil." In the wake of Bush's decision to engage in pre-emptive regime change in Iraq, it is hardly surprising that Pyongyang and Tehran concluded that they might be next on Washington's hit list unless they could effectively deter an attack. Yet, neither country could hope to match the conventional military capabilities of a superpower. The most reliable deterrent--maybe the only reliable deterrent--is to have nuclear weapons. In other words, U.S. behavior may have inadvertently created a powerful incentive for the proliferation of nuclear weapons--the last thing Washington wanted.

Of course, the United States must always be prepared to use military force to defend its vital interests. With regard to elective wars, however, U.S. leaders need to become more aware of the range of possible outcomes--including the risk of unintended side effects. In the security environment of the 21st century, Washington should adopt a security strategy that is both more cautious and more flexible.

North Korean and Iranian leaders noticed that the United States treats nations that possess nuclear weapons quite differently than those that do not. That is not a new phenomenon. Just six years after China began to develop nuclear arms, the United States sought to normalize relations--reversing a policy of isolation that had lasted more than two decades. U.S. leaders show a nuclear-armed Russia a fair amount of respect, even though that country has become a second-rate military power and a third-rate economic power. Washington has treated Pakistan and India with far greater respect since those countries barged into the global nuclear-weapons club in 1998.

Contrast those actions with Washington's conduct toward non-nuclear powers such as Iraq and Serbia. The lesson that North Korea and Iran learned (and other countries may be learning as well) is that possessing a nuclear arsenal is the way to compel the United States to exhibit caution and respect. This is especially true if the country has an adversarial relationship with the United States. After the Iraq War started, North Korea's Foreign Ministry declared: "The Iraqi war shows that to allow disarming through inspection does not help avert a war but rather sparks it. [Only] tremendous military deterrent force powerful enough to decisively beat back an attack . . . can avert a war and protect the security of the country." Those who cheered U.S. military interventions, conservatives and liberals alike, need to ask themselves whether increasing the incentives for nuclear proliferation was a price worth paying--because greater proliferation is the price we are now paying.

And it is not only "rogue states", but even long-established signatories to the Nuclear Non-Proliferation Treaty (NPT) that are considering whether acquiring a nuclear deterrent in the current international climate might be in their interests. That development has provoked a predictable yet unhealthy reaction in the United States. Members of the arms control community have devoted at least as much time and energy to the possibility that stable, democratic, status quo powers such as Germany, Japan, Sweden and South Korea might decide to abandon the NPT and develop nuclear deterrents as they have to the prospect that unstable or aggressive states might do so.

That misguided concern is not confined to the traditional arms control community, often considered to be more liberal. As the North Korean nuclear crisis evolved, some of the most hawkish members of the U.S. foreign policy community became terrified at the prospect that democratic U.S. allies in East Asia might build their own nuclear deterrents to offset Pyongyang. Robert Kagan and William Kristol regarded that prospect with horror: "The possibility that Japan, and perhaps even Taiwan, might respond to North Korea's actions by producing their own nuclear weapons, thus spurring an East Asian nuclear arms race . . . should send chills up the spine of any sensible American strategist."

This attitude misconstrues the problem. A threat to the peace may exist if an aggressive and erratic regime gets nuclear weapons and then is able to intimidate or blackmail its neighbors. But nuclear arsenals in the hands of stable, democratic, status quo powers are not an inherent threat to peace and stability. Kagan and Kristol--and others who share their hostility toward such countries having nuclear weapons--are guilty of embracing a moral equivalence between a potential aggressor and its potential victims.

America's current one-size-fits-all non-proliferation policy is the international equivalent of domestic gun control laws--and exhibits the same faulty logic. Gun control laws have done little to prevent criminal elements from acquiring weapons. Instead, they disarm honest citizens and make them more vulnerable to armed predators. The non-proliferation system is having a similar effect. States like Iran and North Korea are well along the path to becoming nuclear powers, while their more peaceful neighbors are hamstrung by the NPT from countering those moves. The United States must therefore extend its nuclear umbrella, placing America at greater risk, to guarantee the security of allies and clients. Washington's own non-proliferation efforts should focus on delaying rogue states in their quest for nuclear weapons, not on causing problems for peaceful states that want to become nuclear powers to deter unfriendly actors in their neighborhoods.

True, such a changed attitude on the part of the United States might well lead to greater proliferation in some regions. That prospect, however, should not be extrapolated to the nightmare vision of a spiraling arms race and endless proliferation. Nations will make their decisions about whether to become nuclear powers based on a host of factors, and it is not a cost- or risk-free decision--financially, politically or diplomatically.

U.S. policymakers must rid themselves of the notion that all forms of proliferation are equally bad. The United States should concentrate on making it difficult for aggressive or unstable regimes to acquire the technology and fissile material needed to develop nuclear weapons. Even then, American leaders should keep in mind that, at best, U.S. actions will likely only delay, not prevent, such states from joining the nuclear club.

Still, delay can provide important benefits. A delay of only a few years may significantly reduce the likelihood that an aggressive power with a new nuclear weapons capability will have a regional nuclear monopoly and thus the ability to blackmail neighbors. In some cases, the knowledge that achieving a regional nuclear monopoly is impossible may discourage a would-be expansionist power from making the effort to begin with. At the very least, it could cause such a power to configure its new arsenal purely for deterrence rather than for aggression. Although one cannot be certain that the nuclear equilibrium that the United States and Soviet Union achieved on a global basis during the Cold War will be replicated on a regional level, the chances of such a stable environment emerging from a balance of power between regional nuclear states are better than they are in a situation where an aggressive, revisionist state enjoys a nuclear monopoly. Indeed, the recent behavior of India and Pakistan provides some cautious evidence that stable regional nuclear balances may be possible.

So while in the general sense it might be true that fewer nuclear weapons in the world (and fewer countries with nuclear weapons) would be a good thing, such logic is not necessarily absolute. Instead of assuming that all proliferation of nuclear weapons is an inherent danger that must be prevented, policymakers should analyze proliferation and assess its consequences on a case-by-case basis.

There is, of course, one area in which the United States must have a proactive policy: making it clear to new nuclear powers that transferring nuclear technology or weapons to non-state actors is utterly unacceptable because such groups are probably not deterrable. And there are three principal states of concern that fall under the heading of potential malignant proliferators: North Korea, Iran and Pakistan.

The ability of the United States to tolerate a nuclear-armed North Korea is predicated on North Korea not becoming the global supermarket of nuclear technology. An especially acute danger is that Pyongyang may provide either a nuclear weapon or fissile material to Al-Qaeda or other terrorist organizations. North Korea's record on missile proliferation does not offer much encouragement that it will be restrained when it comes to nuclear materials. Perhaps most troubling of all, Pyongyang has shown a willingness to sell anything that will raise revenue for its financially pressed regime, as evidenced by the recent discovery of its involvement in the heroin trade.

Washington should communicate to North Korea that selling nuclear material--much less an assembled nuclear weapon--to terrorist organizations or hostile governments will be regarded as a threat to America's vital security interests. Indeed, U.S. leaders should treat such a transaction as the equivalent of a threatened attack on America by North Korea. Such a threat would warrant putting all options on the table, including military action to remove the North Korean regime. It might even include using nuclear weapons in retaliation for any terrorist nuclear attack. Pyongyang must be told in no uncertain terms that trafficking in nuclear materials is a bright red line that it dare not cross.

Iran's nuclear weapons program is a concern because of that country's ties to terrorist groups. It is no secret that Iran provides funding, safe haven, training and weapons to anti-Israeli groups. But Iran has not supplied terrorist groups with chemical or biological weapons to use against Israel, so it is not clear what incentive Iran would have to give nuclear weapons to terrorists. Indeed, Israel's nuclear arsenal (believed to consist of up to 200 warheads) serves as a powerful deterrent against Iran taking such action.

Iran's terrorist ties were also cited by the 9/11 Commission, which implicated Iran in the 1996 Khobar Towers bombing in Saudi Arabia and cited "strong evidence" that Iran facilitated the transit of several Al-Qaeda members before 9/11. The potential Iran-Al-Qaeda connection is a serious one that deserves further investigation. But without clear evidence that the regime in Tehran was involved in 9/11 or is otherwise supporting or harboring Al-Qaeda, the United States cannot afford another unnecessary war and military occupation like Iraq. But, as with North Korea, it should be made clear to Tehran that transfer of such weapons, material or technology to terrorist groups will be justification for regime change. This policy must be strictly (and swiftly) enforced, not just with Iran but with any other country that aspires to nuclear status.

There is another point that needs to be raised. It is especially troubling that the United States has no direct ties with Iran or North Korea, the two nations that may be the next members of the nuclear weapons club. That is an unhealthy and dangerous situation. In contrast, throughout the Cold War, when the United States and Soviet Union had thousands of nuclear warheads aimed at each other and a nuclear conflict would have resulted in certain destruction of both societies, the two adversaries did not cut off relations. Despite a hostile relationship, the United States maintained an embassy in Moscow and engaged in normal diplomatic relations without ever conceding the fundamental legitimacy of the Soviet system. Eventually, the two powers developed a crisis hotline and adopted other confidence-building measures. By creating normalized relationships with nations with nuclear aspirations, Washington would reduce the danger of miscalculation.

Another benefit of normal diplomatic relations with rogue states is the increased likelihood of better intelligence about a country's nuclear program. Iraq is an important example. The United States had virtually no intelligence assets on the ground to provide first-hand information on the status of Iraq's nuclear program. Instead, decisions were based on second-hand information--primarily from Iraqi exile groups. But the reliability of that information was always uncertain. And--whether for the right reasons or wrong ones--information provided by UN weapons inspectors was not deemed accurate or reliable, and therefore was not trusted.

So, however unsavory it might seem, a more productive approach to U.S. non-proliferation efforts would be to develop better and closer relations with the very regimes that are cause for concern--rather than isolating them, as is currently the case. There is, after all, something to be said for the maxim attributed to Sun Tzu: Keep your friends close but your enemies closer.

Pakistan also demonstrates the limitations of current non-proliferation thinking. Although the current regime is considered an ally in the War on Terror and has helped capture some important Al-Qaeda operatives, the prospect of that country's nuclear weapons falling into the hands of radical Islamists must be planned for. Pakistan is also a concern because so many nuclear efforts in other countries (such as North Korea, Iran and Libya) were tied to a nuclear bazaar created by Pakistani scientist A. Q. Kahn, who has been hailed as a national hero by Pakistani President Pervez Musharraf. Unfortunately, neither the traditional non-proliferation approach nor pre-emptive war is a real solution to this problem. Instead, U.S. efforts should focus on creating better security and command and control over Pakistan's nuclear weapons to prevent them from being used by terrorists. Continuous pressure must also be exerted on Pakistan to make sure that leakage of weapons and materials does not occur. In that vein, there may be lessons to learn from the Nunn-Lugar cooperative threat-reduction program to safely secure Russian "loose nukes" that could be transferred to the Pakistani nuclear arsenal.

U.S. policymakers must think beyond traditional non-proliferation policy. That policy may have served us reasonably well in the past, but a rapidly changing global security environment is rendering it obsolete and potentially counter-productive. We can no longer cling to the NPT and all it symbolizes as the answer to all the varied problems of nuclear proliferation. Instead, we need a large policy toolbox with a variety of tools. That involves a tacit admission that the NPT has probably outlived its usefulness--at least in its current form. No policy lasts forever. In its nearly four decades of existence, the NPT has achieved some significant results, most notably in reversing South Africa's decision to become a nuclear power and delaying proliferation in a number of regions. But the emergence of Israel, India and Pakistan as full-blown nuclear powers and of North Korea and Iran as threshold nuclear states shows that the traditional non-proliferation regime centered around the NPT is a waning asset.

Some aspects of existing U.S. nuclear policy remain viable. We can continue to rely on the ability of America's vast nuclear arsenal to deter attacks on the American homeland by other nuclear powers. Nation-states have fixed addresses and leaders of those countries understand that an attack on the United States would be met with certain retaliation. America deterred the Soviet Union under Josef Stalin and China under Mao Zedong. We can deter new nuclear adversaries as well.

Although proliferation of nuclear weapons and the need to deter new nuclear powers are not welcome prospects, we must be realistic and recognize the likelihood that the number of nuclear powers in the international system will increase in the coming decades and that many of those new members of the global nuclear club will be unsavory regimes. Washington's non-proliferation efforts should concentrate on delaying rogue states in their quest for nuclear weapons, not on badgering peaceful states that may want to become nuclear powers for legitimate security reasons. The problems confronting a focused non-proliferation policy are daunting enough without continuing the vain effort to prevent all forms of proliferation.

Ted Galen Carpenter is vice president for Foreign and Defense Policy Studies at the Cato Institute and the author, most recently, of The Korean Conundrum (2004), with Doug Bandow. Charles V. Peña is director of Defense Policy Studies at the Cato Institute and an analyst for MSNBC.