President Bush laid out his administration's vision yesterday for winning the war in Iraq, acknowledging that the U.S. military has suffered "setbacks" but asserting that it is making unmistakable progress in training Iraqi security forces -- a mission he vowed will not be cut short by political pressures on the homefront.

"As the Iraqi forces gain experience and the political process advances, we will be able to decrease our troop levels in Iraq without losing our capability to defeat the terrorists," Bush told an audience of midshipmen at the U.S. Naval Academy in Annapolis. "These decisions about troop levels will be driven by the conditions on the ground in Iraq and the good judgment of our commanders -- not by artificial timetables set by politicians in Washington."

While Bush appealed for patience, the House minority leader announced hers was at an end. Rep. Nancy Pelosi (D-Calif.) became the first congressional leader to endorse a call to begin withdrawing U.S. troops from Iraq, following the path laid out two weeks ago by Rep. John P. Murtha (D-Pa.).

Pelosi said she was offering her own view, not speaking for the Democratic caucus, but added that her conversations with colleagues suggest that "clearly a majority of the caucus supports Mr. Murtha" and his plan to immediately bring home the 160,000 U.S. forces in Iraq.

In a speech aimed at countering such opposition and bolstering what polls show is flagging enthusiasm for the war among the public, Bush described what he called a record of growing proficiency by Iraqi military and police forces, which he said will allow U.S. troops to reduce their role in day-to-day combat operations. His voice choked with emotion at times, he said an immediate withdrawal or a precise schedule for doing so would vindicate terrorists.

"To all who wear the uniform, I make you this pledge: America will not run in the face of car bombers and assassins so long as I am your commander in chief," Bush said.

The president's speech coincided with the release of a 35-page document outlining his administration's strategy for winning the war. Administration officials said the report was compiled from declassified portions of long-standing war plans. The "National Strategy for Victory in Iraq" says that the administration is working toward winning the war on three fronts: by training Iraqi security forces, by helping the nation establish a democracy, and by targeting economic development and rebuilding efforts in areas of the country cleared of insurgents.

The speech and release of the strategy document come as Bush's approval ratings have dropped to new lows and several polls show a majority of the public now regards the war as a mistake, even if most people believe the United States should secure Iraq before leaving. It was this latter group, administration officials said, that Bush especially wanted to reach, to try to convince them that there is an end in sight even if the date is uncertain.

White House aides have said that before Iraqis elect a permanent government on Dec. 15, Bush will deliver several more speeches detailing his administration's vision for winning the war. Bush warned that U.S. involvement in the war probably will not end in complete triumph. Instead, he said, U.S. troops will leave when Iraqis are prepared to assume the fight.

Several leading congressional Democrats dismissed the speech and the strategy document as warmed-over versions of Bush's rhetoric on Iraq.

"After nearly 1,000 days of war in Iraq, our troops, their families and the American people deserve more than just a Bush-Cheney public relations campaign," said Senate Minority Leader Harry M. Reid (D-Nev.). "They deserve a clear strategy with military, economic and political measures to be met in order to successfully complete our mission."

Pelosi's move was the most notable. She had considered endorsing Murtha's withdrawal resolution immediately after he presented it last month. But she decided to hold back for fear that a proposal drafted by Murtha, a defense hawk from the Democratic Party's moderate wing, would quickly be tarred as the product of her more liberal wing.

At the time, an anticipated cascade of Democratic endorsements for Murtha's position did not materialize, as Democrats cautiously waited to see the proposal's impact. In the ensuing days, the Democratic leadership came under criticism from its activist base for timidity. Aides scheduled a news conference expecting Pelosi later to simply criticize the president's Iraq speech, but she announced yesterday morning she would endorse Murtha's resolution.

Tomorrow, Pelosi will join Murtha in Boston at a Democratic fundraiser. And leadership aides say that when Congress returns from its Thanksgiving recess, they expect that dozens more Democrats will support Murtha's proposal.

Not all Democrats were critical of Bush. Sen. Ken Salazar (Colo.) said the speech was "a step in the right direction, and it begins to address the Senate's call for a successful exit strategy."

Republicans, meanwhile, were supportive, saying Bush had pointed the way to victory. "The president clearly and concisely laid out a plan for success in Iraq," said Senate Majority Leader Bill Frist (R-Tenn.).

In his remarks, Bush continued to equate the war in Iraq with the nation's larger battle against terrorism. He acknowledged that those fighting the United States are largely Iraqi, but added that the most lethal among them are foreign fighters bent on targeting Americans everywhere.

"This is an enemy without conscience, and they cannot be appeased. If we were not fighting and destroying this enemy in Iraq, they would not be idle," he said. "They would be plotting and killing Americans across the world and within our own borders."

Although he exuded a determined optimism, Bush did not express the unbridled confidence that he demonstrated when he addressed Naval Academy graduates here just over six months ago. Then, he triumphantly declared: "We are winning the war on terror."

Bush acknowledged that training Iraqi troops has proved to be painstaking, marked by success and failure as the U.S.-led coalition has had to shift its emphasis from training troops to fight an external enemy to an internal one.

Still, he said, a security force with some units that once fled from battle is making progress. He said there are more than 120 Iraqi army and police battalions with 350 to 800 men each combating the insurgency. Forty of those units, he said, are capable of taking the lead in combat operations, with U.S. support. The Iraqis are even operating a small air force and navy, he said.

Bush brushed off critics who say that only one Iraqi battalion is capable of working without any outside help. "To achieve complete independence, an Iraqi battalion must do more than fight the enemy on its own," he said. "It must also have the ability to provide its own support elements, including logistics, airlift, intelligence, and command and control through their ministries. Not every Iraqi unit has to meet this level of capability in order for the Iraqi security forces to take the lead in fighting against the enemy."

Bush cautioned that victory will require continued sacrifice. He became emotional as he read a letter left on the laptop computer of Marine Cpl. Jeff Starr, who was killed while fighting in Ramadi this year.

"If you're reading this, then I've died in Iraq," Bush read, his voice cracking. "I don't regret going. Everybody dies, but few get to do it for something as important as freedom. It may seem confusing why we are in Iraq, but it's not to me. I'm here helping these people, so they can live the way we live."

Staff writer Jonathan Weisman contributed to this report.

President Bush greets midshipmen at the U.S. Naval Academy in Annapolis after presenting his vision for winning the war in Iraq.

Decisions about troop levels will not be driven by "artificial timetables" set by politicians, the president said.