Yet the ringing endorsements of Nato solidarity yesterday from Tony Blair and Robin Cook cannot hide a growing and disturbing fact: Washington and London risk putting themselves on a collision course over the question of sending infantry into Kosovo.
The squabble could end up making life all the worse for hundreds of thousands of refugees still at the mercy of the Serbs inside Kosovo and being used as human shields as Nato steps up its bombing campaign.
The spat is all the more surprising because of the hitherto very close ties between Downing Street and the White House, celebrated in daily telephone calls, policy seminars and familial closeness between "Tony" and "Bill". But no amount of "Third Way weekends" can hide the differences.
Neither London nor Washington wants a full-scale invasion, and neither wants to end the air war. But some officials in Britain believe that threatening to push harder on the ground would make it possible to ease up in the air and reduce the civilian casualties that are mounting daily. America does not. Britain wants to accelerate planning. America does not.
Nor is it a row over substance, officials on both sides underline, but presentation - so far. Yet as a consequence of its persistence and moral fervour, Britain is in danger of creating a serious argument. In the view of some in Washington, Britain has repeatedly tried to steer the United States towards a more aggressive land strategy for the war. America will not allow its forces to be put in Kosovo except as part of a peace-keeping force, or be railroaded into making commitments until it is ready.
The disagreement goes back to Tony Blair's evening visit to the White House before the Nato summit last month, when he and his weary officials clustered into the Oval Office to put their case after a transatlantic flight. But Mr Clinton deferred repeatedly to Sandy Berger, his hard-nosed National Security Adviser, and Mr Berger would not budge.
Everyone is agreed that if and when a deal is signed with Belgrade, ground forces - under Nato command, but with a United Nations cover - would enter Kosovo and return the refugees. More troops would be needed than originally thought - perhaps 50-60,000, with perhaps 10-15,000 of them Americans. Planning for this force is under way. But Britain is pushing for early decisions, before there is a deal, and before it is clear under what conditions a force would enter Kosovo.
The difference between Washington and London is one of tone, strategy and motivation. There is broad support for the war in Britain, so Mr Blair and Mr Cook can afford to be more bellicose. They also seem to believe that pushing Belgrade harder - by hinting at a willingness to put in infantry - will cut short the air war. And they see the war as a moral issue.
The US believes that the bombing, now up to 700 sorties a day, is working; that it will press Slobodan Milosevic to a deal in the next few weeks; and that raising any alternatives will confuse the diplomacy, split Nato and undermine domestic support for the campaign. In America, the war is characterised as not just about moral issues but also a pragmatic conflict involving issues of national and international interest.
US policy has emerged from three competing interests, and it attempts to balance them all. First, there is the strong moral case for intervention put by Madeleine Albright, Mr Clinton's Secretary of State and herself a refugee from genocide. Second, there are the pragmatic arguments of White House staff against a ground war, and to limit the possibility of US casualties. Third, there is the military case against a ground war but in favour of aggressive air strikes - as aggressive as possible. This is the strategy pursued by General Wesley Clark, Nato's Supreme Commander in Europe.
It is not just still-raw memories of Vietnam or political cowardice that militates against the aggressive use of ground forces to win the war. The Pentagon is not keen, for a start: the army generals do not believe that invasion would work, except with massive force in an operation that is almost impossible to imagine. Diplomatically, Washington knows that at least three Nato governments would probably collapse if it tried to push the war on in this way. It has already antagonised Moscow almost beyond the point of no return.
Militarily, the ghost of Bosnia still stalks the corridors in Washington and London. Then, America pushed for air strikes while the Conservatives put British forces on the ground as part of a UN force. As far as the Americans are concerned, that proved ground forces could simply become hostages to fortune.
There is no constituency in Washington for a land war, or even the aggressive use of US forces on the ground. Most Americans would no more willingly see their sons die in Kosovo than Britons would allow theirs to die in Rwanda. Congress is irretrievably split, unable in recent votes to back the current strategy, escalation or an end to the war. It will be a hard fight for Mr Clinton to get permission from Congress even for a peace- keeping force.
Americans do not necessarily see Mr Blair's crusade as a heroic struggle for good. Many think he is arguing for Americans to be killed in a war that is not theirs. Unlike Mr Blair, Mr Clinton has to listen to the opposition: they control the purse strings and the right to declare war.
Sending Mr Cook to Washington is an opportunity to ease the disagreements. The long-planned trip will be used to present a united face as often as possible, and efforts were under way to arrange joint appearances with Ms Albright to show there is no divide.
There are key decisions to be made in the next month, leading up to the crucial G8 summit of the West and Russia on June 18-20. Nato has started planning for the peace-keeping force in Kosovo, and commitments will soon be needed from the US for a new and larger force. Britain wants a substantial US presence, but there is a strong argument in the US that the force should be largely European.
There are also discussions on how to handle Kosovo's political future. There is an emerging view in Washington that Mr Milosevic must be given some latitude to help him to back down; and there is a continuing view in the White House that ultimately, only he can do the deal that will end the war.
Britain has sometimes seemed to lean more in the direction of removing Mr Milosevic. If the current row is not rapidly smoothed over, it risks making these differences all the harder to bridge.Reuse content