In a letter sent to Mr. Bush on Friday, Senate Majority Leader Harry Reid and House Speaker Nancy Pelosi urged him to begin pulling troops out of Iraq in four to six months. They also asked the president to begin shifting the mission of U.S. forces there from combat to training and logistical support of the Iraqis.
"Adding more combat troops will only endanger more Americans and stretch our military to the breaking point for no strategic gain," Pelosi, D-Calif., and Reid, D-Nev., wrote a day after their party took control of Capitol Hill.
"We are well past the point of more troops for Iraq," they said.
The Democrats' criticism of a troop buildup was not new. But the letter underscored a new reality for Mr. Bush: With the new congressional leadership, his Iraq policy will be challenged at every turn by lawmakers.
Meanwhile, Mr. Bush is shaking up his top military and diplomatic teams in Iraq, as he prepares to unveil his new war strategy in a speech to the nation next week.
Gen. John Abizaid, the top U.S. commander in the Middle East, and Gen. George Casey, the chief general in Iraq, both are expected to leave their jobs in coming weeks.
Adm. William Fallon, currently the top U.S. commander of the Pacific, will replace Abizaid, and Lt. Gen. David Petraeus, who was in charge of the training of the Iraqi military, will replace Casey, CBS News correspondent Gloria Borger reports.
The appointments were expected to be announced later Friday.
CBS News has also learned that Zalmay Khalilzad, the U.S. ambassador to Iraq, will be nominated to become the new ambassador to the United Nations, replacing John Bolton.
Ryan Crocker, a veteran American diplomat who's now the U.S. envoy to Pakistan, was expected to replace Khalilzad in Iraq.
Also, retired Vice Adm. Mike McConnell, a veteran of more than 25 years in intelligence, was named Friday by Mr. Bush as national intelligence director. He succeeds John Negroponte, who moved into the long-vacant job as top deputy to Secretary of State Condoleezza Rice.
Each of the personnel changes comes on the heels of Defense Secretary Robert Gates replacing Donald H. Rumsfeld, the architect of the unpopular war.
Besides ushering in new personnel, Mr. Bush on Friday was to discuss his plans for the Iraq war privately with more than a dozen senators, a list that includes some of his biggest critics as well as his most ardent supporters.
Briefings with lawmakers were expected to continue through next week, culminating in a meeting with bipartisan leadership on Wednesday, according to lawmakers and aides.
"One thing is for certain: I will want to make sure the mission is clear and specific and can be accomplished," Mr. Bush said Thursday.
Mr. Bush spoke with Iraqi Prime Minister Nouri al-Maliki in a secure video hookup for nearly two hours Thursday. The president said he sought assurances from al-Maliki that he would do what's necessary to protect Iraqis against rising sectarian violence.
"I believe Prime Minister Maliki has the will necessary to make the tough decisions," the president said.
Mr. Bush appeared Thursday with German Chancellor Angela Merkel and recounted some of his discussions with al-Maliki. The president said he talked with the prime minister about the final moments of Saddam Hussein's life, when the deposed Iraqi leader was taunted before being hanged Saturday and then filmed dangling from a rope.
"My personal reaction is that Saddam Hussein was given a trial that he was unwilling to give the thousands of people he killed," Mr. Bush said. "I wish, obviously, that the proceedings had gone on in a more dignified way."
CBS News national security correspondent David Martin reports that military commanders have told Mr. Bush they are prepared to execute a troop surge that would put about 9,000 soldiers and Marines into Iraq, with another 11,000 on alert outside the country.
Two Army brigades, about 7,500 troops, would go into Baghdad. Two Marine battalions, about 1,500 troops, would be sent into the western province of al Anbar, heartland of the insurgency, although the commandant of the Marine Corps was recently quoted as saying he didn't see a need for more battalions.
Lawmakers said Thursday they were skeptical of such a plan.
"My conclusion was that it would be a mistake to send more troops to Baghdad," said Sen. Susan Collins, R-Maine. "I think the sectarian violence there requires a political, not a military solution."
This concern was echoed by Abizaid in testimony on Capitol Hill in November. He said 20,000 more troops could be deployed, but that the Army and Marine Corps are too taxed to sustain the increase for long.
Giving Fallon and Petraeus the top military posts in the Middle East would help Mr. Bush assert that he is taking a fresh approach, and help pave the way for him to turn policy there in a new direction.
As with Abizaid, Casey also has expressed reservations about the potential effectiveness of boosting troop strength in Iraq. He told reporters in Iraq last month that he is "not necessarily opposed to the idea" of sending in more troops, but said any increase would have to "help us progress to our strategic objectives."
Besides military, Mr. Bush's new plan for Iraq is expected to contain economic, political and diplomatic components.
Given the need to reduce high unemployment and draw Iraqis away from Shiite militias and the Sunni insurgency, the president is considering loans to businesses. He is looking at getting Iraqis into short-term jobs by proposing a significant increase in the discretionary funds that military commanders can use for reconstruction projects.