NEW YORK // World leaders poured into Manhattan this weekend in the run-up to what is expected to be one of the best-attended UN General Assembly meetings in history, with high hopes for progress on Middle East peace, tackling climate change and nuclear disarmament. Amid the diplomatic cacophony, Barack Obama will make his UN debut as US president and share the world body's stage with such political mavericks as Libyan leader Muammer Qadafi and Iran's president Mahmoud Ahmadinejad.
After a tough summer of fielding rebukes about his weak performance, the UN secretary general, Ban Ki-moon, is pinning his political aspirations on Tuesday's summit designed to jump-start progress on addressing climate change. The UN leader expressed his "deep concern" over the slow pace of negotiations, but said the "largest ever forum" of world leaders discussing global warming showed a collective commitment to "work for the future of this whole world, all of humanity".
In uncharacteristically frank language, he singled out the US and China, two of the world's biggest polluters, as "key countries which can make a great impact" on talks towards hammering out a successor to the 1997 Kyoto Protocol. With only three months left before 180 nations gather to seal the deal in Copenhagen, Mr Ban's summit is something of a gamble: an informal chat between world leaders across round-table discussions, rather than the UN's typically long-winded oratories.
But there is plenty to overshadow the South Korean diplomat's novel meeting, with Mr Obama elevating nuclear disarmament to the top of his UN agenda by selecting the topic for the first ever Security Council summit to be chaired by a US president. On Thursday, the 15-nation body will debate a US-drafted resolution calling for all countries with atomic weapons to scrap their stockpiles - pointing to the permanent, nuclear-armed members of the council: the US, Russia, China, the UK and France. Delegates will also highlight India and Pakistan, which have not signed the 1970 nuclear Non-Proliferation Treaty but nonetheless possess atomic arsenals, Israel, which is assumed to possess nuclear warheads, and the hotly debated programmes of Iran and North Korea.
Mr Ban describes a "very rare momentum" behind the debate, with the Conference on Disarmament breaking a 12-year stalemate in May and a bilateral deal between the US and Russia to cut weapons stockpiles the following month. Mr Obama's announcement on Thursday to shelve plans for an Eastern European missile shield, devised under the administration of George W Bush, sends a powerful message of co-operation to Moscow ahead of the meeting.
Likewise, the White House alternative of boosting missile defence across south-eastern Europe, Turkey and Israel points instead to the threats posed by Iran's current ballistic missile arsenal. Yet Mr Ahmadinejad's presence does not guarantee further rapprochement between Washington and Tehran, with Susan Rice, the US ambassador to the UN, saying there is no meeting scheduled between Mr Obama and Iran's leader.
Ms Rice said the council's five permanent members and Germany will meet Iran on the sidelines, although Tehran has said it is unwilling to discuss its atomic programme, which it claims is designed to generate electricity. The US is concerned that Tehran might be developing nuclear warheads, and Mr Ahmadinejad further alienated western countries on Friday with his latest polemic, describing the Holocaust as a "mythical claim". The US secretary of state, Hillary Clinton, kept open the prospect of further sanctions against Tehran, saying "we will soon see if the Iranians are serious" about negotiations during a speech at the Brookings Institution, a Washington-based think tank, on Friday.
Middle East peace looked set to remain an ever-elusive goal after America's special envoy to the region, George Mitchell, returned from Israel on Friday without securing a deal to halt construction and remove Jewish settlements on Palestinian soil. Speculation was rife that Mr Obama would moderate talks between Israel's prime minister, Benjamin Netanyahu, and the Palestinian president, Mahmoud Abbas, on the sidelines of the assembly.
But Ms Rice said on Friday she was "not in position to announce anything" after Mr Mitchell returned, having failed to secure the moratorium on settlement-building that was needed to draw the Palestinians back to the bargaining table. On Myanmar, Mr Ban sent a cautious approval to the ruling junta on Friday, saying he "welcomes the release of a limited number of political prisoners" among the 7,114 convicts released last week.
The isolated military regime is sending its highest-level delegation to the annual UN meeting in more than a decade, headed by the prime minister, Gen Thein Sein. Another UN concern, the triumphalist attitude of Sri Lanka's government following victory over Tamil separatists after 25 years of civil war in May, remains problematic. The UN's undersecretary general for political affairs, Lynn Pascoe, criticised the detention of 300,000 Tamils during his visit to the island last week, securing another government pledge to release the refugees from military-run camps by the end of January.
For Jeffrey Laurenti, a UN watcher for more than two decades, assembled world leaders will be cautiously assessing whether America's "change in mood" under Mr Obama heralds a longed-awaited "change in policy". "This is the first General Assembly session since George Bush left office, so you have a fundamentally different mood set by the largest most influential guarantor of the whole UN system," said Mr Laurenti, a policy expert from The Century Foundation, a US think tank. "This is Obama's stage in front of the entire world community - so this becomes the opportunity to see whether his asserted commitment to multilateralism and engagement can actually produce results."