Britain's relationship with America is "one-sided" and Tony Blair is routinely ignored by President George Bush, a senior US official has said.
Blair has been Bush's closest ally since the 11 September attacks
Kendall Myers, a senior analyst at the State Department, described Britain's attempts to influence US policy as a "sad business", the Times reported.
Mr Myers reportedly said he felt "a little ashamed" at Mr Bush's treatment of the prime minister.
Mr Blair has been a close ally of Mr Bush since the 9/11 attacks.
The official - a specialist in British politics - made the comments at an academic forum at Washington DC's School of Advanced International Studies on Tuesday.
He reportedly said that despite Mr Blair's attempts to influence the Bush administration's policy, "we typically ignore them and take no notice - it's a sad business".
Mr Myers said that Britain's role as a bridge between the US and Europe was now "disappearing before our eyes".
And he went on to describe the relationship between the US and Britain.
"It was a done deal from the beginning, it was a one-sided relationship that was entered into with open eyes... There was nothing, no payback, no sense of reciprocity."
Mr Myers admitted that the growing unrest in Iraq was also affecting relations across the Atlantic.
"It's a bad time, let's face it," he is quoted as saying. "We have not only failed to do what we wanted to do in Iraq, but we have greatly strained our relationship with Britain."
As a result, he predicted relations between the White House and Downing Street would break down.
He said: "What I think and fear is that Britain will draw back from the US without moving closer to Europe. In that sense London's bridge is falling down."
Downing Street has not commented on the matter.