By Nick Assinder
Political correspondent, BBC News website
The so-called special relationship between Britain and the US was already under intense scrutiny as a result of the current Middle East conflict.
So revelations that America is using Prestwick airport as a staging post for flights delivering bunker busting bombs to Israel could not have come at a worse time.
New pressure on the special relationship
And public protests from Foreign Secretary Margaret Beckett that she is "not happy" with the US and that proper procedures may not have been followed have done nothing to calm widespread anger at the revelation.
Scottish Nationalist leader Alex Salmond has deplored the move, saying it is further evidence that Britain is being used as America's "aircraft carrier".
And he has insisted that, even if the correct procedures had been followed, the flights would still be objectionable on principle.
"I think we should be saying no, but of course that would require an independent foreign policy as opposed to merely acquiescing in everything that the US chooses to do," he said.
Liberal Democrat leader Sir Menzies Campbell has joined the attack, saying it was further evidence that Britain was being "taken for granted" by the US.
And Sir Stephen Wall, a former foreign policy adviser to Tony Blair, has written in the New Statesman magazine that Britain has lost moral authority because of the prime minister's belief he "has to hitch the UK to the chariot of the US president".
Beckett has only complained about procedures
What has made all this criticism particularly sharp is the claimed failure of the Rome peace conference after Britain stood alone with the US in opposing a call from 13 other countries and UN Secretary General Kofi Annan for an immediate ceasefire.
While the two countries insisted such a call would have been pointless unless the conditions for such a ceasefire had been agreed, others claimed they had given Israel a green light to carry on what they believe is a campaign to defeat Hezbollah once and for all, whatever the casualties.
And, of course, the row comes after that famous overheard conversation between George Bush and Tony Blair which saw the president greeting the prime minister with "Yo, Blair" and appearing to dismiss his offer to visit the region himself.
Some have seen Mrs Beckett's publicly-expressed anger at America as an attempt to show some independence.
And it is right that, under agreements dating back to the Second World War, US flights have been allowed to stop-off in the UK.
The airport said it provided logistical support to military flights
But, following the on-going row over rendition, it is this agreement that has been questioned rather than whether the US followed the right procedures.
And the affair has only added to pressure on the prime minister, on the eve of a visit to see the president in Washington, to put some distance between London and Washington.
But, thanks to the prime minister's stance after 11 September and his support for - and involvement in - the Iraq war alongside the US, most believe he is inextricably bound to President Bush.
And, in any case, the prime minister has never shown any signs of doubt that the relationship is the single most important one for the UK to sustain.
He is unlikely, therefore, to allow the row over the use of Prestwick to undermine that.