WASHINGTON (CNN) -- Top Democrats have expressed concern over President Obama's plan to draw down nearly two-thirds of U.S. forces in Iraq by August 2010, while some key Republicans are offering praise.

House Speaker Nancy Pelosi earlier this week questioned the need to keep 50,000 troops in Iraq until 2011.

At issue: Obama plans to leave between 35,000 to 50,000 residual forces in the war-torn country, serving in a training or advisory role to the Iraqi military.

All U.S. troops have to be out of Iraq by December 31, 2011, under an agreement the Bush administration signed with the Iraqi government last year. There are currently 142,000 U.S. troops in Iraq.

House Speaker Nancy Pelosi, D-California, indicated earlier this week that the residual force Obama is planning to leave in Iraq is too large.

Pelosi on Wednesday told MSNBC's Rachel Maddow: "I don't know what the justification is for 50,000, a presence of 50,000 troops in Iraq. ... I do think that there's a need for some. I don't know that all of them have to be in [the] country."

Pelosi clarified her concerns after Obama announced the plan at an event Friday at Camp Lejeune, North Carolina. iReport.com: Do you think troops should be pulled, or should numbers increase?

"As President Obama's Iraq policy is implemented, the remaining missions given to our remaining forces must be clearly defined and narrowly focused so that the number of troops needed to perform them is as small as possible," Pelosi said in a press release. "The president's decision means that the time has come at last for Iraq's own security forces to have the prime responsibility for Iraq's security."

Rep. Lynn Woolsey, D-California, co-founder of the Out of Iraq House Caucus, was critical of the plan.

"I am deeply troubled by the suggestion that a force of 50,000 troops could remain in Iraq beyond this time frame," she said in a statement Friday. "Call such a troop level what you will, but such a large number can only be viewed by the Iraqi public as an enduring occupation force. This is unacceptable."

Rep. Dennis Kucinich, D-Ohio, said that while he supports Obama's "step in the right direction," the new troop plan does not "go far enough."

"You cannot leave combat troops in a foreign country to conduct combat operations and call it the end of the war.  You can't be in and out at the same time," Kucinich said in a release Friday.

And top Senate Democrats echoed some of their House colleagues' skepticism.

"That's a little higher number than I expected," Majority Leader Harry Reid, D-Nevada, said Thursday.

The third-ranking Senate Democrat, Sen. Charles Schumer of New York, said, "It has to be done responsibly, we all agree. But 50,000 is more than I would have thought."

On Thursday afternoon, the president briefed bipartisan leaders from the House of Representatives and Senate -- including Sen. John McCain, R-Arizona, at the White House about the troop plan.

Sen. Carl Levin, D-Michigan, chairman of the Senate Armed Services Committee, said that 50,000 is "somewhat larger" than what he expected. However, he said he has always believed "a few tens of thousands" of troops would be needed for noncombat missions such as training and fighting terrorism.  Watch Obama announce the new Iraq plan »

Before the White House meeting, Sen. Dick Durbin of Illinois, the No. 2 Senate Democrat and a close Obama ally, said he was anxious to get the troops home. But he defended the administration, saying it is "trying to strike the right balance" between ending the war and maintaining stability in Iraq.

Rep. John McHugh of New York, the top Republican on the House Armed Services Committee, said later that Obama assured him the plan to withdraw all combat forces will be revisited if conditions on the ground in Iraq deteriorate.
what do Democrats question what is the size of the residual force? what did obama announce?
President Obama's plan 35,000 to 50,000 plans to leave between 35,000 to 50,000 residual forces in the war-torn country, serving in a training or advisory role to the Iraqi military.
question: what do Democrats question, answer: President Obama's plan | question: what is the size of the residual force?, answer: 35,000 to 50,000 | question: what did obama announce?, answer: plans to leave between 35,000 to 50,000 residual forces in the war-torn country, serving in a training or advisory role to the Iraqi military.