Obama to pull out most Iraq troops by August 2010

In a speech at a Marine Corps base, he said the US "combat mission" in Iraq would officially end by that time.

But 35,000 to 50,000 of the 142,000 troops now in Iraq will stay on into 2011 to advise Iraqi forces, target terror and protect US interests.

Mr Obama praised the progress made but warned: "Iraq is not yet secure, and there will be difficult days ahead."

The president recognised that the conflict had been "a long war" and paid tribute to the US forces who have served in Iraq over the past six years and their families.

"Thanks to the sacrifices of those who have served, we have forged hard-earned progress, we are leaving Iraq to its people, and we have begun the work of ending the war."

He also announced that his administration would increase the numbers of soldiers and Marines, in order to lessen the burden on those now serving, and was committed to expanding veterans' health care.

Some Democrats -- including House Speaker Nancy Pelosi -- have expressed concern that the residual force Obama is planning to leave in Iraq is too large.

Sen. John McCain, R-Arizona, however, said in a speech on the Senate floor that he believes Obama's decision is "reasonable" and that he is "cautiously optimistic that the plan that is laid out by the president can lead to success."

McCain, the ranking Republican on the Senate Armed Services Committee, said that a "failing situation in Iraq has been arrested and reversed" due to the "dramatic success of the surge strategy."