What a difference a year makes.

When President Obama spoke at the United Nations a year ago, he called for having an “independent, sovereign state of Palestine” by this year’s meeting. Palestinian officials have said that his statement was one reason they decided to push for statehood in this year’s General Assembly. “If he said it, he must have meant it,” Palestinian president Mahmoud Abbas can be heard to say in a radio ad airing last week.

However, this year President Obama has led an effort to prevent the Palestinians from pursuing that goal. His remarks at the opening of the General Assembly gave far stronger support to Israel’s case than ever before. Afterwards, Palestinian officials expressed disappointment and confusion, and some went so far as to suggest that Mr. Obama’s remarks were politically motivated to appease the “Jewish lobby.”

Zead Ramadan, the head of the Council on American-Islamic Relations (CAIR) in New York, explained that the Palestinians have given up on Mr. Obama. They “have relied on the moderation of the U.S. for over 40 years to no avail.” And, “I reckon the Palestinian response to an American veto [of a resolution establishing a Palestinian state] is ‘You know, we were right. We were right in going to the United Nations because the U.S. really doesn’t want us to be a state.’”

Regardless of the fact that the president is correct—a “fiat” by the U.N. will not achieve the goal of “two states living side by side in peace”; only an agreement between Israel and the Palestinians can lead to that—he faces more Middle East protests should he veto, as promised, any unilateral resolution that reaches the Security Council. But it is evident already that his many efforts to raise America’s standing in the Muslim “world” through apologies, televised speeches and direct engagement have failed. America’s image among Muslim publics has not improved. According to a recent Pew survey, it’s gotten even worse—including in places like Jordan, Turkey and Pakistan with whom we’ve had close relations. Most Muslims even disapproved of Washington’s response to the Arab Spring.

It is no surprise, then, that President Obama was not interrupted even once with applause during his speech this year, as he was last year and in 2009. His ability to galvanize and motivate the “international community” behind his causes has waned, and along with it American leadership and influence.

The president had an opportunity to reverse that slide when he spoke before the General Assembly. Unfortunately, he squandered it. With every important head of state listening, he delivered a lecture filled with platitudes and stump-speech overtones. He laid out no agenda for the year or initiatives that the United States will champion at the U.N. other than finally calling for Security Council sanctions on Syria. He spent as much time pointing out his own “successes” as he did praising the U.N.’s ideals.

The irony is that for many of the examples he mentioned to show progress since he became president—the winding down of operations in Iraq and Afghanistan, the doing away with Osama bin Laden and the overthrowing of Qaddafi—Mr. Obama relied on hard military power, not soft power, and least of all not “smart power.” If the Bush administration had subscribed to Obama’s philosophy, it’s a good bet none of these gains would have been achieved.

The issue that claimed the most time in his speech was of course that of the Palestinian state. His belated support for Israel was tempered by his playing the moral-equivalence card (“each side has legitimate aspirations” and “deadlock will only be broken when each side learns to stand in each other’s shoes”)—as though actions taken in self-defense to protect people from missile attacks have as much legitimacy as launching barrages of missiles at elementary schools and public markets.

After making his case that the Palestinian issue could not be solved by the very institution he had just lauded, Mr. Obama gave lip service to a laundry list of favorite U.N. causes, such as climate change, that coincidentally are of special interest to his domestic constituents.

President Obama is arguably the most pro-U.N. and internationalist American president in decades. He may sincerely believe that his reticent, one-state-among-many approach is what’s needed to improve America’s standing in the world. If anything, it is making the United States and the world more insecure. His penchant to let others take the lead, to join “international consensus” regardless of implications for U.S. sovereignty or security, and to rely more on “soft-power” diplomacy and aid has done little to convince countries like Iran and North Korea to fall in line.

Such an approach is, however, more likely to make his oft-repeated line in the speech that “peace is hard work” not only self-fulfilling, but also the phrase that historically comes to define his presidency, much as “peace through strength” defined Ronald Reagan’s. Only in Obama’s case, the “hard work” is not working.

Demonstrating real American leadership at the United Nations is hard work; but without it, there is little chance the U.N. can achieve any of its lofty goals. The type of leadership Americans want to see is someone who challenges the institution and its member states to take the hard road—to stop, for example, coddling dictators and despots who abuse their people and their positions. They want to see someone who is unafraid to promote tough policies that unleash political and economic freedom, no matter how unpopular they may be in Paris or Moscow. And they want to see someone who is willing to say out loud that business as usual is no longer acceptable, and that without substantive course corrections, the U.N. may find itself facing the tough love of U.S. withholdings again.

That message would resonate.

Yes, it would no doubt be roundly criticized by some at home and abroad who care more about the appearance of multilateralism than the results. But it also would be cheered—by other leaders who’ve been hoping for that kind of principled American leadership; by millions around the world who live in fear of their governments; and by the majority of Americans who want people everywhere to share in the blessings of liberty and are willing to help give them the chance.