Tony Blair is to embark on a frantic round of diplomacy in an attempt to persuade the world's richest nations to agree a new plan to help the poorest at the G8 summit in July.
The Prime Minister will meet the leaders of Italy, Germany and the US, thought to be most likely to scupper a historic agreement, proposed by Britain, to tackle Africa's problems by doubling aid to the developing world from $50bn (£27bn) to $100bn a year.
British officials deny that the proposal, first made by the Chancellor, Gordon Brown, is in trouble, saying that the aim of Mr Blair's tour is to "keep up momentum" before July's meeting at Gleneagles. Despite his bad back, he is expected to clock up more than 50,000 miles in the next four weeks.
But there are growing fears that the three countries may regard Britain's blueprint as too ambitious and costly, and be more concerned about economic problems closer to home.
Mr Blair's talks will also cover proposals to improve governance in Africa and climate change, two main priorities for Britain's year in the rotating presidency of the G8.
The Prime Minister will begin his offensive in Rome on Friday, when he will meet Silvio Berlusconi, his Italian counterpart. He will also travel to Washington for talks with President George Bush, their first meeting since November, and to Moscow to meet Vladimir Putin, the Russian President. He will also meet the German Chancellor, Gerhard Schröder, and the French President, Jacques Chirac, who is more sympathetic. He will also hold video conferences with the prime ministers of Canada and Japan.
America has never been keen on the British aid plan and Mr Blair's attempt to rally President Bush behind it could be undermined by the scepticism in Rome and Berlin. Some officials fear that the US will feel less pressure to back it if European Union countries are divided.
But Blair aides say that countries are not yet declaring their hand in what will be a complex negotiation. They insist that the pressure could cut both ways: if Mr Bush throws his weight behind the British proposals, it could act as a lever on Germany and Italy.
Announcing the diplomatic offensive yesterday, Mr Blair's official spokes-man said: "We have set out an ambitious agenda for the G8 and this is the time for detailed negotiation. The important point is that no one in the G8 disputes that Africa and climate change must be the priorities. We believe at this stage we are achieving progress, but we still have some way to go."
Mr Blair is determined to ensure that the G8 countries sign up to a package of debt relief for Africa, and a plan to boost good governance and economic reform on the continent. He also hopes to make progress on climate change, despite America's failure to ratify the Kyoto treaty, limiting greenhouse gas emissions.
His spokesman added: "This is a proper negotiation and when you are driving a proper negotiation it's generally counter-productive to comment on the positions of other countries. People will not take up final positions at this stage."
Downing Street pointed to the United Nations Millennium Summit in New York in the autumn and the World Trade Organisation meeting in Hong Kong in December as areas where progress could be made. But, it said: "The G8 is a major point in that process and we are going for it."