Brown's attempts to meet star of the show end in the kitchen

Gordon Brown has made five abortive attempts to secure a formal one-to-one meeting with Barack Obama during his four-day visit to the US this week, it emerged yesterday.

Although British officials denied that the Prime Minister had been snubbed, all he has managed so far is a 15-minute conversation with the President in the kitchens of the UN headquarters in New York as they left the building together. Officials said their on-the-hoof discussion covered Afghanistan and the global economy.

The two men are due to appear together at a Friends of Pakistan event in New York today, but no press conference is planned. Sources said Mr Brown ordered his government to match Mr Obama's pledge to help the world's poorest countries combat swine flu in an attempt to secure a joint appearance. The UK will provide up to £23m.

Diplomats insist the President's diary is crowded during a hectic week. However, he is finding time for one-to-one talks with the leaders of China, Russia and Japan.

Mr Brown received a boost when several other leaders pledged to follow his lead by attending the climate conference in Copenhagen in December. Lars Lokke Rasmussen, the Danish Prime Minister, said he was prepared to invite all leaders to take part.

Mr Brown's plan for industrialised countries to contribute $100bn a year by 2020 to help developing nations become low-carbon economies was also endorsed at a dinner of 23 leaders in New York.

With his speech delayed by more than two hours by Col Gaddafi's earlier appearance, Mr Brown reaffirmed support for the UN's founding principles after the Libyan leader had theatrically tossed aside a copy of the UN Charter and denounced its treatment of smaller nations.

"I stand here to reaffirm the United Nations Charter, not to tear it up," Mr Brown said to applause. "I call on every nation here to support its universal principles."

The Prime Minister issued a stark warning to world leaders to grasp the nettle in the next six months on "five urgent challenges" – climate change, terrorism, nuclear proliferation, poverty and shared prosperity. "We are at a point of no return," he said.

Confirming that Britain would put its Trident nuclear weapons system on the table in talks on global disarmament next spring, he added: "In line with maintaining our nuclear deterrent, I have asked our [the Cabinet's] national security committee to report to me on the potential future reduction of our nuclear weapon submarines from four to three."

Yesterday, Mr Brown launched a £3.2bn scheme to bring an NHS-style healthcare system to Africa. Britain will contribute £250m to help African nations abolish fees for health care which affect millions of pregnant women, mothers and children. An estimated three million children have died as a result of "user fees".

The Prime Minister hailed the programme as "an historic step towards the goal of universal health care in Asia and Africa." He said: "We cannot let mothers die through lack of finance and through the persistence of user fees."

* Mr Brown made a 15-minute appearance at a dinner for the Appeal of Conscience Foundation, at which he received a World Statesman of the Year award for stabilising the financial system.