U.S. President Barack Obama greets military personnel on Friday after disembarking Air Force One en route to Marine Corps Base Camp Lejeune, N.C. (Charles Dharapak/Associated Press)

U.S. President Barack Obama announced plans on Friday for the "responsible" removal of all U.S. combat forces from Iraq by the end of August 2010, but warned the country "is not yet secure" and may face "difficult days ahead."

The president announced two end dates to the mission, with some 100,000 combat troops being pulled out by Aug. 31, 2010, while some 35,000 to 50,000 support troops will stay in the country until Dec. 31, 2011.

"Let me say this as plainly as I can: by Aug. 31, 2010, our combat mission in Iraq will end," Obama told an assembly of marines at North Carolina's Camp Lejeune on Friday.

"There will surely be difficult periods and tactical adjustments. But our enemies should be left with no doubt: this plan gives our military the forces and the flexibility they need to support our Iraqi partners, and to succeed."

'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 this war.'—U.S. President Barack Obama

The presence of the smaller force will serve to train Iraqi forces and conduct targeted counterterrorism efforts, while also being able to provide a security presence in Baghdad for elections next December, he said.

The span of the pullout presents a longer time frame than Obama, a vociferous critic of the Iraq war, had pledged during the presidential election campaign last year.

"The bottom line is it is beginning," the CBC's Paul Hunter reported from Washington on Friday.

U.S. 'pursues no claim' to Iraqi territory, sovereignty

In the meantime, he said, U.S. troops will face more danger in the months to come.

"But 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 this war," he said.

The president also offered a message to the Iraqi people, saying the United States "pursues no claim on your territory or your resources."

"In years past, you have persevered through tyranny and terror, through personal insecurity and sectarian violence," Obama said.

"And instead of giving in to the forces of disunion, you stepped back from a descent into civil war, and showed a proud resilience that deserves respect."

He warned there will be those who will try to disrupt the path toward a peaceful Iraq, and "insist that Iraq's differences cannot be reconciled without more killing."

"But hostility and hatred are no match for justice," Obama said. "They offer no pathway to peace, and they must not stand between the people of Iraq and a future of reconciliation and hope."

The pullout, Obama said, will coincide with increased U.S. diplomacy throughout the Middle East, including "principled and sustained engagement" with nations such as Iran and Syria.

"We can no longer deal with regional challenges in isolation," he said.

Obama also pledged to increase the number of soldiers and marines in the armed forces to relieve the burden on those serving and their families. He also promised his administration would expand and improve health care for veterans, as well as invest in new ways to help identify and treat soldiers with post-traumatic stress disorder and brain injuries.

"You and your families have done your duty; now a grateful nation must do ours," he said.

McCain backs Obama's 'significantly different' plan

The plan is expected to garner wider support from military officials and Republicans who have pleaded with the new administration for more flexibility in withdrawing forces.

In an interview on Friday, John McCain, the Republican senator who lost the presidential election to Obama in November, said he supports the plan because it is "significantly different" from the 16-month timetable Obama advocated during his campaign.

But according to U.S. media reports, some senior figures within Obama's own party have expressed anxiety about the number of forces remaining beyond next year.

"That's a little higher number than I expected," Senate majority leader Harry Reid told reporters on Thursday before joining other congressional leaders in a meeting with Obama at the White House.

More than 4,250 U.S. military members have died in the war since it began in March 2003, according to an Associated Press tally.

With files from the Associated Press