UNITED NATIONS, New York — As protesters jeered Iranian President Mahmoud Ahmadinejad outside his five-star hotel near Central Park here Tuesday, U.S. President Barack Obama and other world leaders warned that the world is running out of patience with Iran's nuclear ambitions.

"America wants to resolve this issue through diplomacy, and we believe that there is still time and space to do so. But that time is not unlimited," Obama said in a 30-minute speech to the UN General Assembly. "Make no mistake: a nuclear-armed Iran is not a challenge that can be contained. It would threaten the elimination of Israel, the security of Gulf nations, and the stability of the global economy."

UN Secretary General Ban Ki-moon, speaking before Obama, argued against unilateral military action and, though he didn't mention Israel by name, said a pre-emptive military strike "would be devastating."

Ahmadinejad, who told a UN meeting on Monday that Israel ought to be "eliminated," will get his turn at the General Assembly podium about midday Wednesday.

"The shrill war talk of recent weeks has been alarming," Ban said. "I reject both the language of delegitimization and threats of potential military action by one state against another."

Still, Ban said, "Iran must prove the solely peaceful intent of its [nuclear] program."

Israeli Prime Minister Benjamin Netanyahu has been pressing Obama and the U.S. to establish some "red lines" which, if crossed by Iran, would provoke a military response. Netanyahu speaks to the General Assembly Thursday and is expected to reinforce his case.

Obama, though, has resisted agreeing to any such conditions, repeating at the UN what he has said elsewhere, that "the United States will do what we must to prevent Iran from obtaining a nuclear weapon."

Netanyahu wanted to meet with Obama while in New York but the White House said Obama's schedule is full.

Obama did have time to tape an appearance Monday on the daytime talk show The View, which was broadcast Tuesday about the same time Obama spoke to the UN.

Prime Minister Stephen Harper, on the other hand, will meet with Netanyahu here Friday. Harper will be in New York Thursday to receive the Appeal of Conscience Foundation's award for World Statesman of the Year. Harper, like the leaders of China, Germany, South Korea and many other countries, will not address the UN General Assembly. Foreign Affairs Minister John Baird will speak on Canada's behalf.

Obama's Republican challenger Mitt Romney was also in New York Tuesday. In his speech at a meeting of the Clinton Global Initiative, Romney promised he would tie U.S. foreign aid to foreign policy goals such as open markets and democratic governance.

Former president Bill Clinton introduced Romney. Obama also spoke to the same group after his UN address.