Britain's army has been stretched by missions in Iraq and Afghanistan and is not in a position to deploy any more soldiers, army chief Richard Dannatt said in an interview broadcast on Sunday.
Dannatt's comments come at a time of growing calls at home for Britain to withdraw its 5,500 troops from southern Iraq and as a force of more than 7,000 in Afghanistan battles Taliban militants in the south of the country.
"The army is certainly stretched. And when I say that we can't deploy any more battle groups at the present moment that's because were trying to get a reasonable balance of life for our people between time deployed, time on training and time in barracks," Dannatt told BBC television.
"Currently the time in barracks isn't as much as I would like. We can be busy, we can be stretched, we can run hot - provided we are looking after individuals and, critically, our soldiers feel valued and supported and thanked for what they are doing," he said during a visit to Afghanistan.
Britain is expected to pull out of its base in central Basra in southern Iraq soon and hand over responsibility for security to Iraqi forces, leaving about 5,000 British troops at a sprawling base at the nearby airport.
Forty-one British troops have died in Iraq this year, on track to exceed the 53 killed in 2003 when Britain joined US forces in an invasion to topple Saddam Hussein.
Talk is rife that Britain's new prime minister, Gordon Brown, could announce a withdrawal of troops from Iraq as soon as October although some analysts say this could harm London's relations with Washington.
Britain's Independent on Sunday newspaper said army generals have told Brown they have done all they can in southern Iraq and the force should withdraw without delay.