Baghdad: A security pact that sets a timetable for troops to leave Iraq requires a shift in how the US carries out combat missions during its remaining time in the country, the top US military commander in Iraq said on day.

General Ray Odierno said in a written statement to troops that they would be receiving new rules of engagement but that there would be no change to their ability to protect themselves and the multinational force.

The security pact, "though, will require a subtle shift in how we plan, coordinate and execute combat missions throughout Iraq," Odierno said, adding that under the new terms of agreement, US troops will coordinate and execute all operations with the approval of the Iraqi government and implement them through the Iraqi security forces.

Odierno released the statement a day after Iraq's three-member presidential council signed off on the pact, removing the last legal barrier so that the agreement can take effect January 1.

The security pact requires US troops leave Iraq by January 1, 2012. It also requires American soldiers withdraw from Iraqi cities by the end of June 2009.

Withdrawal plan

Under the agreement, Iraq will gain strict oversight over the nearly 150,000 American troops now on the ground, representing a step toward full sovereignty for Iraq and a shift from the sense of frustration and humiliation that many Iraqis feel at the presence of American troops on their soil for so many years.

The security agreement replaces a UN mandate that gave the US-led coalition sweeping powers to conduct military operations. The pact is still subject to approval by Iraqi voters in a referendum by the end of July.

Odierno also said US troop would continue to conduct operations in Iraq against Al Qaeda and other extremist groups.

"But we must do so with respect for the Iraqi Constitution and laws, and we must continue to treat all Iraqi citizens with the utmost dignity and honour," he wrote.

Odierno said the US will phase in the shift in responsibilities of the military to preserve security gains.

American troops, though, continue to be a target of insurgents. In an attack on Thursday, two American soldiers were killed when a suicide driver detonated an explosive-laden car near an Iraqi checkpoint in the northern city of Mosul, military spokesman Lt Col. Dave Doherty said.

Iraqi police said eight people were wounded, most of them civilians.