copyright 2009, The Washington Post UNITED NATIONS -- The U.N. Security Council unanimously adopted a U.S-drafted resolution Thursday morning that affirms many of the steps President Obama plans to pursue as part of his vision for an eventual 'world without nuclear weapons.' In a first for a U.S. president, Obama presided over the 15-member meeting, joined by such leaders as Russian President Dmitry Medvedev, Chinese President Hu Jintao and British Prime Minister Gordon Brown. The meeting marked only the fifth head-of-state summit in U.N. history, and Obama's presence was intended to signal the importance of the issue for the administration. Addressing the leaders, Obama said nuclear weapons pose a 'fundamental threat' to the world. '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 and would badly destabilize our security, our economies and our very way of life,' he said. While the resolution passed on a 15-0 vote, the United States failed to get approval from China and Russia to cite Iran and North Korea by name. In a diplomatic fudge, the text therefore refers only to Security Council resolutions concerning the countries. Obama mentioned the two countries by name in his speech, saying he was not trying to single out any country but that 'international law is not an empty promise.' North Korea tested a second nuclear weapon this year, and Iran has resisted greater international oversight for its nuclear program. Iran says its nuclear activities are for peaceful purposes, but the United States and other major powers fear they are a cover for a weapons program. Obama is pressing for a new worldwide treaty to halt production of weapons-grade uranium and plutonium and strengthen the global Non-Proliferation Treaty, which has limited the spread of nuclear weapons for decades but now is in danger of fraying. French President Nicolas Sarkozy was more pointed than Obama in his criticism of Tehran, listing offers made by world powers to Iran in 2005, 2006, 2007, 2008 and this year, with no real response from the Islamic Republic. 'There comes a time when stubborn facts will compel us to take a decision if we want a world without nuclear weapons,' he said. 'We live in a real world, not a virtual world,' and the world must act if Iran does not respond at a crucial Oct. 1 meeting in Geneva. 'If we have the courage to affirm and impose sanctions together against those who violate resolutions of the Security Council, we will be lending credibility to our commitment towards a world with fewer nuclear weapons,' Sarkozy said. Brown also declared that 'far tougher sanctions' must be imposed on Iran if it continues to enrich uranium in defiance of previous Security Council resolutions. In closing remarks at the end of the two-hour meeting, Obama declared that ridding the world of nuclear weapons was a 'difficult but achievable goal.' Although Libya currently has a seat on the Security Council, Libyan leader Moammar Gadhafi did not appear at the meeting, the only leader of a member country not to do so. He had been scheduled to speak as Libya's de facto head of state, but the Libyan statement was read by the country's U.N. ambassador instead. There was no immediate explanation for the switch. The morning session of the Security Council, whose rotating chair is held this month by the United States, came amid a two-day U.N. conference that will strongly push for a worldwide ban on nuclear tests, officials said. For the first time in a decade, a U.S. delegation will attend the biennial U.N. session on the Comprehensive Test Ban Treaty, which has been ratified by 149 countries but lacks the support of nine critical governments, including several declared and undeclared nuclear powers. Secretary of State Hillary Rodham Clinton, who is leading the delegation, is expected to commit the U.S. government to trying to ratify the treaty, which was defeated in the U.S. Senate in 1999. Obama's agenda marks a sharp departure from the policies of his predecessor, George W. Bush, who was generally skeptical of the reliability and value of arms-control treaties. Obama has said the new approach is necessary because rogue states and terrorists are trying to acquire nuclear bombs, and the spread of nuclear technology could set off arms races in volatile regions such as the Middle East. Jeffrey Lewis, a nonproliferation expert at the New America Foundation, said the U.N. resolution would represent significant international support for Obama's nonproliferation agenda, which was first outlined in a speech in Prague in April. 'It's great for the president to go and give the speech. It's a heck of a lot more powerful if the other countries with nuclear weapons ... say, `OK, it's also the direction we wish to go,' 'Lewis said. Countries belonging to the Non-Aligned Movement have objected to the resolution's insistence that nuclear violators be brought to the attention of the Security Council, diplomats said. Under current practice, countries that ignore their nonproliferation obligations are first referred to the International Atomic Energy Agency, which can then bring the matter before the council. White House officials said the language would give the Security Council more authority to enforce compliance with the Non-Proliferation Treaty. Critics say the Obama administration is placing too much hope in treaties that may not win sufficient ratifications for years nor be fully verifiable. 'They are overselling this, overselling how likely it is to come into force, and how likely it is to be beneficial if it did,' said Henry Sokolski, executive director of the Nonproliferation Policy Education Center. Gaining Senate ratification of the Test Ban Treaty will be critical to Obama's agenda, and diplomats including Ellen Tauscher, the undersecretary of state for arms control and international security, will use the U.N. conference to develop a diplomatic strategy to get other holdouts to soften their opposition, officials said. 'Other countries have said, if we ratify, they'll ratify,' said a senior administration official, speaking on condition of anonymity. Such promises could make it easier to convince skeptics in the U.S. Senate that voting for the treaty is worthwhile, officials said. Indonesia has pledged to ratify the treaty if the United States does so, and China could quickly follow suit, according to analysts. Other holdouts include Egypt, Israel, India, Pakistan, Iran and North Korea. North Korea conducted a nuclear test this year and is considered unlikely to approve the pact any time soon. Iran has signed the treaty but has not ratified it. Supporters of the treaty say that by ratifying it, the United States could help isolate and increase pressure on countries that don't do so. 'We are not going to be able to credibly call on other states to take on additional nonproliferation responsibilities if we don't fulfill what other states consider U.S. disarmament commitments,' said Darryl Kimball, director of the Arms Control Association. -- Sheridan reported from Washington. Staff writer Colum Lynch contributed to this article. 