WASHINGTON — Launching a new effort to rally support for the war in Iraq, President Bush yesterday acknowledged the dangers that U.S. troops face and vowed that their sacrifices wouldn't be in vain.

"I understand how dangerous it is there," he said. "I understand we've got kids in harm's way, and I worry about their families. And obviously, anytime there's a death, I grieve."

The president's sober assessment was part of a White House effort to reassure Americans that he's on top of events in Iraq and is working to bring U.S. troops home. With polls showing growing dissatisfaction with the war, even some fellow Republicans have urged Bush to be more forthright about the difficulties there.

A growing number of lawmakers and military experts are predicting it will be at least two years before Bush can significantly reduce the number of U.S. troops, currently about 140,000. Some lawmakers, including Republicans who supported the war, have proposed setting a timetable to begin pulling out by this fall.

White House aides said the president planned a series of speeches and other events focusing on the stakes in Iraq and his strategy for success.

Bush said "cold-blooded" killers will fail in their attempt to drive the United States out of Iraq prematurely, as he defended the administration's war strategy and also its policies for secretly detaining hundreds of alleged terrorists worldwide.

Bush said those who have lost family in the war must remember two things: "One, we're not going to leave them — not going to allow their mission to go in vain. And two, we will complete the mission, and the world will be better off for it."

Bush did not answer when asked whether he agreed with Vice President Dick Cheney's assessment that the Iraq insurgency, which has killed more than 100 U.S. soldiers since the beginning of last month, is in its "last throes."

Bush, who was briefed earlier in the day by Gen. John Abizaid, the top military commander in Iraq and Afghanistan, suggested that fighting would continue even after American troops left. He didn't offer any timetable for withdrawal, but said his goal was to let Iraqi security forces take over as soon as possible.

"The report from the field is that while it's tough, more and more Iraqis are becoming battle-hardened and trained to defend themselves," Bush said. "And that's exactly the strategy that's going to work."

The president's emphasis on turning over the fighting to Iraqis, rather than on leaving behind a peaceful Iraq, reflects the growing feeling among military commanders that the insurgency can't be defeated on the battlefield. The only real solution, they say, is for the Iraqi people to turn against the insurgents.

"This insurgency is not going to be settled — the terrorists and the terrorism in Iraq is not going to be settled — through military options or military operations," Brig. Gen. Donald Alston, the chief military spokesman in Iraq, told Knight Ridder earlier this month. "It's going to be settled in the political process."

Iraq is likely to be near the top of the agenda today when Bush meets with Senate Republicans at the White House. Some Republican lawmakers have become increasingly vocal about their differences with the president and his advisers.

"Things aren't getting better, they're getting worse. The White House is completely disconnected with reality," Sen. Chuck Hagel, R-Neb., told U.S. News & World Report in this week's issue. "It's like they're making it up as they go along. The reality is that we're losing in Iraq."

Sen. John McCain, R-Ariz., said Sunday on "Meet the Press" that the U.S. effort in Iraq was going to be "a hard slog."

"I think we should tell people it's not going to be a short — I'd rather say two or three years, and be surprised a year from now, than say, 'Everything's fine,' and then be disappointed a year or two from now," McCain said.

As part of his rallying effort, Bush will highlight progress in Iraq at a meeting Friday with Iraqi Prime Minister Ibrahim al-Jaafari. The president also plans a major speech next week to mark the first anniversary of the transfer of authority from the U.S. military to Iraqi civilians.

Bush, who answered a few questions after meeting at the White House with leaders from the European Union, also defended the detention of suspected terrorists at the U.S. Navy base at Guantánamo Bay, Cuba. He urged journalists to visit the facility, which the human-rights group Amnesty International has criticized as a "gulag."

"These are people picked up off the battlefield in Afghanistan," Bush said of the detainees. "Many of those folks being detained — in humane conditions, I might add — are dangerous people."