World leaders agreed Thursday on the sweeping goal of a planet free of atomic weapons, but faced continued divisions over details of one of their thorniest challenges, Iran's nuclear program.
The United Nations Security Council approved a resolution proposed by President Obama setting a series of goals to eliminate nuclear weapons, ban production of the fissile material used to make them, outlaw atomic tests and safeguard stockpiles in the meantime.
The resolution also advocates action against nations that put civilian nuclear technology to military use in violation of the international Nuclear Nonproliferation Treaty.
It did not name specific countries, but the resolution expressed concern over steps by some nations to develop nuclear programs and weapons.
During the council meeting, leaders singled out Iran and North Korea, with several speakers urging action to restrain the two countries. North Korea already has tested weapons, whereas Iran is accused by U.S. officials and their allies of seeking to develop them.
"Talk of a nuclear-free future is nice, but we are facing two immediate nuclear crises," said French President Nicolas Sarkozy, naming Iran and North Korea. "Iran is violating the Security Council's resolutions right before our eyes."
He was joined by Obama and British Prime Minister Gordon Brown, who urged "far tougher" sanctions against Iran.
The comments came as pressure on the issue intensified. The council's five permanent members -- the United States, Britain, France, Russia and China -- along with Germany are to meet with Iran next week in Geneva in an effort to start talks over Tehran's nuclear program, which Iran says is intended for peaceful, civilian purposes.
The Obama administration claimed progress this week in its push to put pressure on Iran: After a meeting with Obama, Russian President Dmitry Medvedev signaled for the first time that Moscow might agree to stiffer economic sanctions against Tehran. As one of Iran's major trading partners, Russia could exert considerable influence over the Islamic Republic.
However, China opposes sanctions, urging a less threatening solution to the standoff.
"We believe that sanctions and exerting pressure are not the way to solve problems and are not conducive for the current diplomatic efforts on the Iran nuclear issue," Chinese Foreign Ministry spokeswoman Jiang Yu said at a news briefing in Beijing, Reuters news service reported.
But other world powers are pushing for a tight deadline on working out a deal with Iran. Italian Foreign Minister Franco Frattini said he favors giving Tehran until the end of the year to avoid new sanctions. Italy is the current chair of the wealthy Group of 8 nations.
Sarkozy, whose country also is a member of the G-8, agreed with the December deadline.
For Obama, the issue overshadows another top foreign policy priority: Mideast peace. Israeli Prime Minister Benjamin Netanyahu said Thursday in a speech before the General Assembly that unless Iran was restrained, peace in the region would be impossible.
"We want peace," Netanyahu said. "I believe such a peace can be achieved. But only if we roll back the forces of terror, led by Iran, that seek to destroy peace, eliminate Israel and overthrow the world order."
Iranians ridicule charges they are seeking to develop nuclear arms. To underscore the point, Iranian President Mahmoud Ahmadinejad proposed this week that the U.S. and other powers sell Iran enriched uranium for medical purposes, and offered to allow Iranian scientists to discuss their country's program and its needs with international officials.
The offer came in an interview with the Washington Post, and U.S. officials have not responded.
"There exist diplomatic channels for them to be able to make this kind of proposal," State Department spokesman Ian Kelly said.
Ahmadinejad has generally struck a conciliatory note during his visit to the United States, urging Obama not to view him as a threat and offering to negotiate with others in good faith.
Obama presided over the Security Council session Thursday at which 14 of the 15 heads of state and government adopted the measure calling for a world without nuclear weapons and laying the groundwork for future action to reduce nuclear dangers. Libya's leader, Moammar Kadafi, did not attend.
The vote was the result of months of negotiations, and Obama became the first American leader to preside over a full-scale summit of the Security Council. There have been only five such summits in the United Nations' 64-year history.
Obama urged the Security Council members to make sure international law didn't prove to be "an empty promise," while also acknowledging the difficulty ahead.
"We know there are plenty of cynics, and that there will be setbacks to prove their point," Obama told the council. "But there will also be days like today that push us forward, days that tell a different story."
The resolution is only a preliminary victory for a president who has made nuclear disarmament and nonproliferation a personal goal. Many of its provisions reiterate support for past resolutions.
But Obama administration officials and disarmament advocates believe the vote reflects an international recognition of Obama's push, and it came after a month of messages from the White House that the president meant to take action.
Immediately after the vote, Obama urged wide acceptance of the resolution's principles.
"Just one nuclear weapon exploded in a city -- be it New York or Moscow; Tokyo or Beijing; London or Paris -- could kill hundreds of thousands of people," he said. "And it would badly destabilize our security, our economies and our very way of life."
With former secretaries of State George Shultz and Henry Kissinger looking on, Obama quoted former President Reagan:
"A nuclear war cannot be won and must never be fought. And no matter how great the obstacles may seem, we must never stop our efforts to reduce the weapons of war. We must never stop at all until we see the day when nuclear arms have been banished from the face of the Earth."