Tony Blair will try to prevent next month's G8 summit at Gleneagles ending in failure by appealing to US President George Bush to drop his opposition to more aid for Africa and action to tackle climate change.
On a flying visit to Washington today, the UK Prime Minister will reject pressure from Labour and Tory MPs for him to demand a "payback" for his staunch support for America on Iraq.
Instead, he will adopt a "softly, softly" strategy, denying that he wants a "blank cheque" for Africa and stressing that he shares the United States' commitment to tackling corruption in the continent.
As Mr Blair flew to America last night, Downing Street played down the prospects of an immediate breakthrough, saying the Bush administration would not declare its "final position" until the summit in Scotland on 6-8 July.
But Mr Blair is hopeful of nudging a wary President towards a position that would allow Britain to claim some progress at Gleneagles.
Africa and climate change will top the agenda when Mr Blair and President Bush discuss Britain's G8 goals in talks with officials and over a one-to-one dinner at the White House. Mr Blair is also due to meet prominent US campaigners on both issues.
Cherie Blair, who spoke in Washington last night for a reported £30,000 fee, may attend a separate function at the White House.
Chris Grayling, the shadow Leader of the Commons, described Mrs Blair's trip to the White House as "quite extraordinary" because Downing Street had said her separate visit was entirely private.
"This is completely unacceptable and it makes the commercial nature of her visit even more inappropriate. It amplifies my view that she should give the proceeds of her visit to charity," he said.
The Bush administration has poured cold water on Britain's proposal for an international finance facility which would "front load" aid from rich to poor countries.
But Mr Blair hopes the US will make a gesture towards the Make Poverty History campaign by boosting its aid to Africa.
However, President Bush is unlikely to back British calls for the richest nations to sign up to the United Nations target of 0.7 per cent of their national output on aid and may attach conditions about good governance to any extra money.
Despite the turmoil in the European Union over its stalled constitution, Mr Blair will side firmly with Europe on African aid in an attempt to push America further.
The EU has agreed to meet the United Nations goal by 2015.
Progress at Gleaneagles on action to save the planet looks a remote prospect. But Mr Blair is trying to build support for what has been dubbed a "Kyoto lite" treaty which would draw the US, China and India into the international moves to cut carbon emissions.
The Prime Minister's official spokesman suggested that Britain might have to change tack to make progress given the US's opposition to its specific proposals on Africa and climate change.
"You can either have endless discussions on areas we know we are not going to agree on or widen the lens," he said.