Washington: An entire brigade of 3,500 US troops is being lined up to replace British forces as they pull out of southern Iraq, The Sunday Telegraph has learned.
The move, which will put an additional burden on US forces involved in the "troop surge" further north, risks plunging the special relationship between the British and American military to a new low, according to an advisor to President Bush.
Frederick Kagan, one of the architects of the surge strategy, warned that the British departure risked creating "bad feeling" among US troops, some of whom may face extended terms of duty as a result.
He spoke out after the deaths of three British soldiers in Afghanistan, killed by bombs dropped from a US aircraft, placed new strains on the alliance in the other main military theatre.
In an outspoken interview with The Sunday Telegraph, Kagan condemned British politicians for failing to understand how best to tackle extremists, and for refusing to increase the size of the Armed Forces so they could pull their full weight in Iraq.
Details of the number of US troops required to take over were disclosed by a senior British officer, who asked not to be named.
He also revealed that commanders at the Ministry of Defence were "irritated" by the growing criticism from the United States of their handling of Basra.
The British officer said soldiers on the frontline in Iraq shared the frustration of US commanders that "they have not been allowed to do their job".
He said: "At a regimental level they will be delighted to get out. Not because they're tired or battle weary, but because they are fed up of being held in bases and getting shot at."
Kagan, who has just returned from Iraq, said: "It will create bad feeling with American soldiers if they can't go home because the British have left."
His words are a new embarrassment for Gordon Brown at a time when the prime minister is determined to press ahead with troop reductions in Iraq.
Kagan said Britain had withdrawn its troops to barracks to avoid provoking insurgents, rather than working to help the local population throw out militants.
Without naming Brown, he accused British political leaders of using Army overstretch as an excuse to withdraw from Iraq.