Leading article: The United Nations has a chance to fulfil its potential

America has engaged. Now the onus lies with other world leaders

Meetings of the United Nations General Assembly traditionally produce their fair share of grandstanding from world leaders. But their record is meagre when it comes to delivering anything of substance. Will this week's gathering of 120 political leaders in New York be any different?

To his credit, Barack Obama is making a considerable effort to squeeze real progress from this year's meeting on the banks of the East River. Indeed, Mr Obama's schedule over the next few days makes him look more like the UN Secretary General than the American president.

Today Mr Obama will address a special summit on climate change, designed to accelerate talks in advance of December's crucial meeting in Copenhagen on designing a successor to the Kyoto Protocol. He will also make time to bring the Palestinian President, Mahmoud Abbas, and the Israeli Prime Minister, Benjamin Netanyahu, together for talks on the Middle East peace process. Then, on Wednesday, Mr Obama will deliver his first address to the General Assembly. Finally, on Thursday, he will personally chair a Security Council discussion on nuclear disarmament.

Mr Obama plainly has a radically different attitude to the merits of the United Nations than his predecessor in the White House. Where George Bush gave the impression that he would happily see the UN's Manhattan headquarters decamp from America's shores, Mr Obama regards it as a serious forum for tackling some of the most intractable problems facing the world.

It is a commendable shift. But we should bear in mind that the engagement of the White House is no guarantee of harmonious outcomes. Remaking relations with Iran is an example of that. On Wednesday, Security Council foreign ministers will meet to prepare for talks with Iran, which are scheduled to begin next month. But it is easy to see Mahmoud Ahmadinejad, who is due to address the General Assembly on the same day, upsetting such plans, especially if the Iranian President decides to air his ludicrous and offensive theories on the nature of the Holocaust.

The ability of the US to influence talks on a successor to Kyoto should not be exaggerated either. The Obama administration's acceptance of the need for radical action makes a breakthrough in Copenhagen possible. But unless developing industrial nations accept that they too will need to reduce their emissions, no deal will be reached. The attitude of China and India to the threat of global warming is just as significant as that of the US.

It is a similar tale with moves towards nuclear disarmament. Mr Obama has prepared the ground by shelving missile defence shield technology and with an offer to reduce the number of American warheads. But it is an overture to which other nuclear powers – from Russia, to India, to North Korea – need to respond.

Obama's engagement with the machinery of the United Nations and the forum it provides opens up exciting new diplomatic possibilities. But, ultimately, it will be up to those leaders in attendance this week to decide whether such gatherings become a significant event on the global political stage – or whether they are destined to remain little more than a distracting carnival, while the important decisions are made elsewhere.