Peter Hain has branded the Bush administration the "most right-wing in living memory" and its foreign policy a "failure".
The Northern Ireland and Wales secretary's interview in the New Statesman is awkwardly timed for the prime minister, who was on Thursday meeting US secretary of state Condoleezza Rice for talks about the Middle East.
In remarks which are likely to be seen as criticism of Tony Blair's friendship with President Bush, Hain called for Labour to re-align itself with the Democrats.
"Our sister party is the Democratic Party, so for me the results in November were fantastic," he said, referring to the Republicans losing control of Congress.
Hain, who is bidding to become Labour's next deputy leader, said the Republicans' defeat reflected the failure of their entire 'neo-con' agenda.
"It's not only failed to provide a coherent international policy, it's failed wherever it's been tried," he said.
"And it's failed with the American electorate, who kicked it into touch last November."
But speaking in the Commons, leader of the House and former foreign secretary Jack Straw issued a coded criticism of Hain.
Straw said anyone aspiring to high office should learn to "accept foreign governments as they are" and then seek to work with them.
Number 10 also indicated that it remains important to continue a close working relationship with the US administration.
Rice was stopping off in London to see the prime minister and foreign secretary Margaret Beckett after a three-day tour of Israel and the Palestinian territories.
"The important thing we have taken from our two recent trips to the Middle East is the need for engagement at all levels and by many different people and in many different ways," said the prime minister's spokesman.
"The important thing is we keep talking to each other, not just about impressions on the ground but also how we can help push things forward."
The spokesman said the prime minister would "reflect" on what Rice says and form a view of what his next steps should be.
The prime minister singled out the Middle East as a priority for his final months in office and has said there are "signs of progress" in the region.
