MOSUL, Iraq -- In a festively bedecked dining hall, Defense Secretary Donald H. Rumsfeld served Christmas Eve dinner to dozens of U.S. soldiers, then fed them his view -- with a mix of optimism, caution and emotion -- of why the war that has cost more than 2,150 U.S. lives must be won.

"We will win this war. It's a test of wills, and let there be no doubt that is what it is," he said. Rumsfeld told the troops that "generations before you have persevered and prevailed, and they too were engaged in a test of wills."

"In this fight, the vast majority of Iraqis stand on the side of freedom," he said over the roar of helicopters flying over a regional U.S. military headquarters that once was a palace of Saddam Hussein.

Rumsfeld, winding up a five-day trip that began in Pakistan and included stops in Afghanistan and Jordan, said the battle for Iraq is part of the wider global war on terrorism, which he called "this long war against terrorism and it will be a long war.

Repeating a theme he struck throughout his visit, Rumsfeld cautioned against an early exit from Iraq. He said that giving up would mean allowing terrorists to impose "their dark vision on the rest of the world.

"Let there be no doubt: if the United States were to withdraw from Iraq today the terrorists emboldened by their victory would attack us elsewhere in the region and at home in the United States, he said.

With an emotion that sometimes creeps into his voice when he talks about the human cost of the Iraq war, Rumsfeld said the Christmas season was a time to remember those who have been lost in combat

"You folks have helped liberate some 25 million people for whom hope was never there before," he added.

Before he spoke, Rumsfeld helped serve the soldiers a dinner of rib-eye steak, lobster, crab legs, Cornish game hens and all the seasonal fixings. Grinning widely and wearing a white cooks hat, he worked his tongs as many of the soldiers snapped pictures of him and politely asked for their helpings.

"Steaks the big seller tonight, he declared after the first several dozen soldiers had gone through the line.

It was the second straight year that Rumsfeld served Christmas Eve dinner to troops in Iraq.

Last year it was in Baghdad at a time of hope that the election of an interim government in January would deal a heavy blow to the insurgency, which nonetheless remained resilient and deadly throughout 2005.

On his current visit, Rumsfeld and senior military commanders appeared even more optimistic that Iraqi progress on the political front will soon translate to greater success in neutralizing, if not defeating, the insurgency.

It was clear from Rumsfeld's three-day visit that the U.S. military is shifting its focus from fighting the war to preparing the Iraqis for the day when they will be left to fight it largely on their own.

Lt. Gen. John Vines, commander of Multinational Corps-Iraq, told reporters Saturday in Baghdad that there is no hard assurance that the Iraqis will manage the transition without collapsing into civil war, although he is optimistic. He said it may take 30 days or more before he can judge whether the Iraqis are putting together a truly representative and viable government, based on the constitution that voters approved Oct. 15.

Gen. George Casey, the top U.S. commander in Iraq, said on Friday that he foresees a period of "churn" in the political process. That is why he has decided to keep the 2nd Brigade of the 1st Armored Division at its staging base in Kuwait rather than sending those soldiers home. The brigade originally was scheduled to deploy to Iraq, but Casey put them on hold after reaching Kuwait, as part of a decision announced Friday by Rumsfeld to reduce the number of combat brigades in Iraq next year from 17 to 15.

Before he left Baghdad on Saturday, Rumsfeld said in an interview with Fox News that he had a private dinner Friday with a group of leading Iraqi politicians. He said they had a lively discussion.

"You know people didn't do that here four years ago," he said. "If people expressed themselves they would be killed and put into these mass graves, imprisoned and as a result it created a whole element of fear that prevented people from expressing themselves, the way that these folks were expressing themselves at the dinner."