The British military hoped to withdraw troops from Iraq within about a year and London wanted to focus on the war in Afghanistan, a US defense official said on Tuesday.
British officials had told US counterparts the British military was "near the breaking point" due to long deployments in Iraq and weak retention of personnel, said the official, asking not to be identified.
The official's comments offered the first hint Britain's military may have a timetable for withdrawal in mind.
"It's about a year, give or take a few months," the official said.
But another US defense official played down the withdrawal issue, and no immediate comment was available from UK Prime Minister Tony Blair's Labour government.
The official said British discussions about troop levels were part of regular, internal military reviews and that the British government had not approached senior US officials with adjustment plans or timetables.
On Sunday, British Defense Secretary Des Browne said Britain was "quite far down" the road toward transferring responsibility for security in Iraq to Iraqi forces but British troops would leave only when the job was done.
About 7,200 British troops are based in southern Iraq and Blair has been US President George W. Bush's closest ally over Iraq.
Britain has launched a large new operation in Afghanistan this year, and commanders have acknowledged they had hoped to accelerate force reductions in Iraq.
Blair and Bush face intense pressure at home over Iraq because of the unrelenting violence.
An opinion poll published on Tuesday showed more than 60 percent of Britons want their troops to be withdrawn this year, and surveys show Bush's policy on Iraq may cost his Republican Party control of Congress in Nov. 7 elections.
A British withdrawal could put more stress on US forces, already facing equipment and funding shortfalls and the possibility of repeat tours of duty in Iraq.
Britain has handed over authority to Iraqi forces for two of the four provinces in its area of responsibility in the south.
Meanwhile, a senior UK defense ministry official insisted on Tuesday that British forces were "stretched" but not "overstretched" by deployments in Iraq, Afghanistan and other hotspots.
Bill Jeffrey, a top civil servant, admitted that the military was under strain but declined to say how close it was to being unable to cope with current demands.
Jeffrey said the rest period between missions was the measure used to judge how much the military was under strain -- and fewer than one in seven soldiers -- is getting the amount of rest time the ministry thinks necessary between intensive operations.
"The word overstretch implies that what we are doing now is not sustainable. We do not believe that to be the case," Jeffrey told the House of Commons defense committee scrutiny body.
"The assessment is that our armed forces are stretched but not overstretched," he said, calling it "very hard to say" how close to that point British forces had got.
"There's no reason to suspect we cannot undertake our commitments," he said.
However, he added: "If there were serious proposals now to engage in further major deployments ministers would, I am sure, decide they were not able to do it."
He said troop reductions next year should ease the situation.
Britain has around 5,000 troops stationed in Afghanistan and about 7,000 on duty in southern Iraq.