A test for both Mr Blair and the special relationship

There is one obvious benefit to the Government's decision to shelve a referendum on the European constitution: more pressing global challenges, such as tackling poverty in Africa and climate change, have shot to the top of the agenda in Tony Blair's search for a lasting political legacy. That the Prime Minister is now staking his reputation as chairman of the G8 group of rich nations on an ambitious deal on both issues when world leaders meet in Scotland next month is welcome. Today in Washington, as part of his efforts to prepare the ground for a summit in Gleneagles that he has already claimed will be "historic", Mr Blair will try to persuade the US President to support him.

There is one obvious benefit to the Government's decision to shelve a referendum on the European constitution: more pressing global challenges, such as tackling poverty in Africa and climate change, have shot to the top of the agenda in Tony Blair's search for a lasting political legacy. That the Prime Minister is now staking his reputation as chairman of the G8 group of rich nations on an ambitious deal on both issues when world leaders meet in Scotland next month is welcome. Today in Washington, as part of his efforts to prepare the ground for a summit in Gleneagles that he has already claimed will be "historic", Mr Blair will try to persuade the US President to support him.

This is no easy task. For once - ironically, in light of the EU turmoil of the last week - Britain and the rest of Europe will be closer (certainly on climate change, and on aid for Africa, if not on trade) than Britain and America. Indeed, whatever gloss is put on the outcome of today's talks, it is difficult to sustain hope that the Prime Minister will be able to claim more than a superficial meeting of minds with his US ally.

On Africa, much will be made of Washington's acceptance of the need for debt relief. But the Bush administration has already rejected Gordon Brown's proposed "Marshall Plan for Africa", which would double international aid by setting up a financing facility to issue bonds on world capital markets against future aid budgets. Washington has also ruled out the Chancellor's proposal to part-sell IMF gold reserves to raise billions for the continent.

The differences are not merely of approach but of vision. America is simply not convinced that increasing aid is part of the answer to Africa's plight. Not only has the US government flatly refused to sign up to spending 0.7 per cent of national wealth on aid, a target to which Britain and the other EU nations are formally committed, it would link debt relief to reducing aid by the same amount in the future.

The chances of persuading Mr Bush to drop his short-sighted intransigence on climate change seem even bleaker. Again, the Prime Minister will try to highlight areas of common ground on issues such as scientific research into climate change and renewable energy. But this is no substitute for persuading America to sign up to the scientific consensus that underpins the Kyoto protocol and its targets for cutting greenhouse gases.

Notwithstanding the difficulties, Mr Blair should not give up on his attempts to persuade the United States to see reason. On Africa alone, one only has to look at the support the Make Poverty History campaign has drawn to sense the depth of public feeling in Britain behind this cause. The Prime Minister should have amassed vast political credit with the White House with his misguided support for the conflict in Iraq. It is not unreasonable to ask for payback. Although Mr Bush faces little significant domestic pressure on these issues, he needs to be persuaded that he cannot achieve his own strategic goals, whether in the "war on terror" or the spreading of democracy, if he ignores concerns that are central to others in the international community.

Perhaps in anticipation of a rebuff, the Downing Street publicity machine has tried to lower expectations of success in Washington today. But this is a real test for the so-called special relationship between Britain and America, and for Mr Blair's consistent support for the misadventures of the Bush administration. But it is not just about domestic politics; the world awaits the outcome. And failure to extract some genuine American concessions will cast a long shadow over the gathering in Gleneagles.