Preventing the acquisition of nuclear weapons by additional states and terrorist groups is one of America’s top national-security priorities. The outcome of the ongoing negotiations between the P5+1 (China, France, Germany, Russia, the United Kingdom and the United States) and Iran will have a profound impact on whether the cause of nonproliferation will be strengthened or set back.

Last November, the P5+1 and Iran extended for a second time the interim agreement known as the Joint Plan of Action. The extension ensures that for now the brakes on Iran’s most sensitive nuclear activities remain firmly in place, but neither side believes this arrangement is acceptable in the long term.

Though gaps remain in their positions, the P5+1 and Iran are working hard to reach agreement on a long-term, comprehensive deal. A good deal would verifiably block Iran’s potential paths to becoming the tenth country armed with nuclear weapons. The key is to stringently and verifiably limit Iran’s capacity to enrich uranium, a process that can be used to make reactor fuel or bomb material, and its capacity to amass plutonium for weapons. In return, the P5+1 would take steps to suspend and eventually remove certain nuclear-related sanctions so long as Iran’s nuclear program remains exclusively peaceful.

Skeptics, though, argue that the P5+1’s negotiating position—which envisions a final deal that would allow for a limited Iranian uranium-enrichment program—would undermine nonproliferation by encouraging other states in the region, especially Saudi Arabia, to pursue an enrichment capability. While a deal is highly unlikely to prompt Iran’s regional adversaries to make a mad dash to actually acquire nuclear weapons, the concern is that unless Iran’s nuclear program is dismantled, regional states will build their own domestic enrichment facilities, thereby placing them closer to being able to build nuclear weapons in the future.

However, the concern that an agreement allowing some Iranian enrichment will encourage the practice elsewhere is overblown. The alternative is no comprehensive P5+1 and Iran nuclear deal, which would result in a less constrained—if not unconstrained—Iranian nuclear program with less monitoring. This poses more of a threat to regional security and would be more likely to increase the possibility of a cascade of regional fuel making.

Saudi Nuclear Considerations

Prior to the November 2013 interim agreement, Iran had been expanding its capacity to enrich uranium for more than a decade. However, no state in the region responded by developing enrichment or plutonium reprocessing capabilities—though states such as Saudi Arabia, the United Arab Emirates and Jordan announced their desire to pursue nuclear-energy programs. Logic would thus suggest that a comprehensive deal that not only stops Iran’s nuclear progress, but puts Tehran further away from a nuclear weapon, shouldn’t make other states want to pursue nuclear fuel making any more than they would if the Iranian program was left unchecked.

In addition, as Iran has no doubt learned, developing the capability to produce nuclear fuel is time consuming, technically challenging, expensive and, in a region as volatile as the Middle East, potentially threatening to one’s neighbors.

Take the case of Saudi Arabia, the poster child for concerns about falling enrichment dominoes in the Middle East. Riyadh, a regional rival of Iran, has ambitious plans for nuclear power and long expressed concern about Iran’s illicit nuclear program. Some current and former Saudi officials and royal-family members have warned of matching Tehran’s nuclear-weapons potential and voiced misgivings about the trajectory of the nuclear negotiations.

However, Saudi Arabia’s official position on the November 2013 interim agreement was that it “could represent a preliminary step towards a comprehensive solution to the Iranian nuclear program.” This suggests that Riyadh sees benefits to negotiated limits on Iran’s nuclear program relative to the pre–interim agreement status quo, when Iran’s program was unconstrained.

Meanwhile, Riyadh’s nuclear-power program remains in its nascent stages. Saudi Arabia currently has no nuclear-power plants. Last month, a Saudi energy official announced that a key milestone to install 17 gigawatts of nuclear power by 2032 would be delayed by eight years to 2040. Saudi Arabia’s official position is that it would choose not to enrich or reprocess, capabilities for which it has no near-term practical need. A May 2008 U.S.-Saudi memorandum of understanding on nuclear energy cooperation declared: “Saudi Arabia has stated its intent to rely on international markets for nuclear fuel and to not pursue sensitive nuclear technologies.”

Going back on this pledge in response to a comprehensive deal with Iran would cause much consternation in Washington, including possibly making Riyadh the target of U.S. sanctions. Though Saudi Arabia has expressed concern about U.S. policy toward Iran and other regional-security challenges, such as the Syrian civil war, there is no other country—or technology—that Riyadh’s leaders can turn to that can provide the same level of proven support and protection. In addition, Saudi moves to develop an indigenous fuel-making capability could prompt Iran to reconsider its commitment to the deal. Were the deal to collapse under these circumstances, it would be extremely difficult, if not impossible, to reconstitute a sanctions regime to punish and isolate Iran.

To the extent Saudi Arabia engages in nuclear hedging in response to a nuclear deal, racing to develop an enrichment capability is unlikely to be its first choice. Instead, Riyadh is more likely to develop its civilian nuclear program, which has scarcely gotten of the ground.

No Deal More Likely to Incentivize Enrichment Cascade

Despite the obstacles to pursuing enrichment and reduced incentives for nuclear hedging a comprehensive deal should bring, Saudi Arabia might nevertheless be uneasy in the aftermath of an agreement.

For example, Riyadh could worry that a comprehensive deal leading to the removal of nuclear-related sanctions, but not a prohibition on nuclear fuel-making, would lend international legitimacy to Iran’s enrichment program, thereby enhancing Tehran’s influence in the region. Even if the Kingdom decided it could live with a limited Iranian enrichment program, it might nonetheless be concerned by the fact that the enrichment limits in a comprehensive deal will end at some point, likely after ten to fifteen years.

However, these anxieties must be weighed against the alternatives to a comprehensive deal.

A final deal requiring the permanent dismantlement of Iran’s enrichment program of course would be ideal from a nonproliferation perspective. But it’s not a realistic option, nor is it necessary to prevent a nuclear-armed Iran. Tehran has invested far too much, both financially and politically, to turn back from enrichment now. Furthermore, as Deputy Secretary of State Tony Blinken put it recently, Washington’s P5+1 negotiating partners “are unlikely to stick around in terms of implementing the [existing] sanctions regime if that [no enrichment] has to be the bottom-line test.”

It is also important to remember that the six UN Security Council resolutions calling on Iran to suspend its uranium-enrichment activities do not require Iran to dismantle its enrichment facilities or permanently halt enrichment.

There is little evidence that new unilateral U.S. sanctions or airstrikes against Iran’s nuclear facilities would compel Iran to abandon enrichment. Sanctions have been useful in bringing Iran to the negotiating table, but they have not stopped Iran's program from advancing. According to a December 2013 U.S. intelligence community assessment, “new sanctions would undermine the prospects for a successful comprehensive nuclear agreement with Iran.”

While airstrikes against Iran’s nuclear facilities might temporarily set back the program, the delay would be temporary and run a high risk of convincing Iran to dash to acquire nuclear weapons to prevent such strikes in the future. A ten-to-fifteen-year deal will keep Iran further away from the ability to make enough highly enriched uranium for a nuclear weapon for longer than the alternative of a military strike possibly could.

Even if Iran did agree or was forced to give up its enrichment program, it would still retain the know-how and capability to rebuild the program relatively quickly in the future. The knowledge it has acquired cannot be sanctioned or bombed away. Thus, the incentive Saudi Arabia and other regional adversaries of Iran might have for nuclear hedging behavior would exist under any scenario short of regime change.

Ultimately, insisting on zero enrichment and pursuing new sanctions or airstrikes in an attempt to compel such an outcome would likely be ruinous to both diplomacy and the international sanctions regime. This would increase the risk of a nuclear-armed Iran and the attendant security and proliferation cascade dangers that would come with it. And an Iran with a less constrained nuclear program and faced with a weakened international sanctions regime would be a greater threat to Saudi Arabia’s influence in the region.

Bottom Line

The United States has long sought to prevent the spread of uranium enrichment and plutonium reprocessing programs and it should continue to do so in the aftermath of a comprehensive deal with Iran. The tools of most relevance include security assurances and guarantees, bilateral nuclear cooperation agreements, fuel-supply guarantees, proposals for multinational fuel-supply arrangements and, if necessary, sanctions.

Saudi warnings that it might follow Iran down the path of a nuclear-weapons capability are symptomatic of its distrust of Iran and desire for greater protection from the United States. A comprehensive nuclear agreement with Iran can promote regional security and nonproliferation without barring all Iranian uranium enrichment, if its limits are significant and its verification measures are strong. It is the failure to secure a comprehensive deal to prevent a nuclear-armed Iran that would strike a much larger blow to the global nonproliferation regime.

Kingston Reif is the Director for Disarmament and Threat Reduction Policy at the Arms Control Association. You can follow him on Twitter @KingstonAReif