A US military commander says pulling troops out of Iraq by Christmas would be a "giant step backwards".

Major General Rick Lynch, who commands troops south of Baghdad, was responding to John Warner, the Virginia Republican senator, who has called on President George W. Bush to announce the start of a phased withdrawal next month. Mr Warner, a second world war veteran and former chairman of the Senate armed services committee, said the White House needed to "put some meaningful" teeth into criticisms of the Iraqi government.

"In my battlespace right now...if coalition soldiers were to leave, having fought for that terrain, having denied the enemy of their sanctuaries, what will happen is the enemy would come back," said Gen Lynch. "He'd start building the bombs again, he'd start attacking the locals again, and he'd start exporting that violence into Baghdad and we would take a giant step backwards."

Mr Warner said withdrawing some troops - he suggested 5,000 - would focus minds in the government of Nouri al-Maliki, the Iraqi prime minister, which he criticised for not achieving political reconciliation.


"We simply cannot, as a nation, stand and put out troops at continuous risk of loss of life and limb without beginning to take some decisive action which will get everybody's attention," said Mr Warner, after returning from a trip to Iraq.

Separately, the Los Angeles Times reported on Friday that Gen Peter Pace, the outgoing chairman of the joint chiefs of staff and the US president's most senior military adviser, would advise Mr Bush to cut the US troop presence by half after the troop "surge" wound down. US commanders have made clear the surge cannot be sustained past April because of the strain on the forces.

The Iraq debate is expected to intensify when Congress returns early next month, just before Gen David Petraeus, the top US commander in Iraq, and Ryan Crocker, the US ambassador to Baghdad, present their report on the surge to Congress.

Mr Warner made his unexpected move the same day the Director of National Intelligence released its latest National Intelligence Estimate on Iraq, which concluded that the government was "precarious" and would "struggle" to achieve any political reconciliation over the next year.