Washington ? In a sobering assessment of the Iraq war, President Bush acknowledged Monday that Americans’ resolve has been shaken by grisly scenes of death and destruction, and he pointedly criticized the performance of U.S.-trained Iraqi troops. “No question about it,” he said. “The bombers are having an effect.”

At a year-end news conference, the president also offered a warm testimonial for Defense Secretary Donald Rumsfeld in the face of spreading expressions of no-confidence by GOP senators. Rumsfeld appears “rough and gruff,” Bush said, but “he’s a good, decent man. He’s a caring fellow.”

For 53 minutes, Bush fielded questions on international and domestic affairs. It was his 17th formal news conference, held one day before he flies to the presidential retreat at Camp David for a vacation that will stretch into early next year and include a stay at his Texas ranch.

Bush spoke a day after the deadliest attacks in Iraq since July — killing at least 54 people in Najaf and at least 13 in Karbala — and six weeks before Iraqis vote for a transitional assembly that will choose a president and a government and draft a permanent constitution. American newspapers showed chilling pictures of rebels in the heart of Baghdad executing election workers in cold blood.

“And so the American people are taking a look at Iraq and wondering whether the Iraqis are eventually going to be able to fight off these bombers and killers,” Bush said in perhaps his clearest expression of frustration with Iraqi forces. Bush’s strategy calls for American troops to protect Iraq while local police and soldiers are trained to do the job themselves, eventually allowing the United States to withdraw.

“Now I would call the results mixed in terms of standing up Iraqi units who are willing to fight,” Bush said. “There have been some cases where, when the heat got on, they left the battlefield. That’s unacceptable. Iraq will never secure itself if they have troops that, when the heat gets on, they leave the battlefield.” What is needed, he said, is a better military command structure.

Polls show an erosion in Americans’ confidence that a stable, democratic government will be established in Iraq.

“Polls change. Polls go up, polls go down,” Bush said.

He said he understood why Americans had doubts about Iraq’s ability.

A day after blasts killed dozens of civilians in Iraq, President Bush acknowledged that efforts to put Iraqis in charge of their country's security had brought mixed results. Bush spoke Monday at his year-end news conference at the White House.

“They’re looking on your TV screen and seeing indiscriminate bombings, where thousands of innocent — or hundreds of innocent Iraqis are getting killed.”

But Bush said those pictures did not reflect the fact that 15 of Iraq’s 18 provinces are relatively stable and that small businesses are starting up.

“Life is better now than it was under Saddam Hussein,” he said. “But no question about it. The bombers are having an effect. … They’re trying to shake the will of the Iraqi people and, frankly, trying to shake the will of the American people.”

Bush warned that insurgents would try to delay Iraq’s elections, scheduled for Jan. 30, and intimidate the people.

“I certainly don’t expect the process to be trouble-free,” the president said. “Yet I am confident of the result. I’m confident that terrorists will fail, the elections will go forward and Iraq will be a democracy.”

He said he could not predict when American forces could come home.