"With the Black Watch gone you allow the enemy to operate more freely. I can control some of (the area they vacated), but definitely not all of it," Major Morgan Mann told AFP.

"I think it's an issue" said the officer from the 2nd battalion of the 24th Marine Expeditionary Unit, adding that while a US army unit is set to take over the Black Watch's beat, no firm date has been set for its deployment.

The Black Watch, who at the weekend pulled back to their base in Basra in relatively tame southern Iraq, had patrolled an area on the west bank of the river Euphrates.

"We're not going across the river any more," said Mann, whose unit has a heavily-fortified base in the town of Yusufiyah, on the east bank of the Euphrates about 40 kilometres (25 miles) south of Baghdad.

US commanders say their enemy in the so-called triangle of death is a loose alliance of wealthy former Baathists and extremist religious leaders, criminal gangs and disillusioned men using weapons looted from munitions factories.

Mann's company's area was limited to the area immediately surrounding Yusufiyah while the Black Watch were based at Camp Dogwood, but it has now considerably expanded with their departure.

The British soldiers were sent north on October 27 to assist US troops before American and Iraqi forces launched an assault on the rebel Sunni stronghold of Fallujah on November 7.

The redeployment caused a political uproar in Britain.

Many observers saw the move, barely a week before US elections, as a sop to President George W. Bush by British Prime Minister Tony Blair, his main ally in the Iraq campaign.

Blair denied the move was linked to Bush's bid for re-election, and promised that the Black Watch would be home by Christmas.

The Scottish regiment, which makes up roughly 10 percent of the British contingent in Iraq, lost five men during its mission, four in attacks and one in an accident.