The U.S. Senate has paid tribute to the two-thousand U.S. troops who have died in Iraq. Some opposition Democrats used the occasion to step up their criticism of the Bush administration's handling of the war there.

The Senate Tuesday observed a moment of silence in honor of the U.S. soldiers who died in Iraq since the U.S.-led war began in 2003.

Senate Majority Leader Bill Frist said those troops sacrificed their lives for the cause of freedom.

"Because of their determination, Saddam Hussein now faces the trial of his life; because of their resolve, the Iraqi people are exercising their right to self-rule; and today because of their bravery, today Iraq has a new constitution, a historic milestone on the march toward freedom and the fight against terror," Senate Frist said.

Senator Frist spoke shortly after the Pentagon announced that Staff Sergeant George Alexander Jr. of Texas died of injuries sustained when a roadside bomb detonated near his vehicle in the town of Samarra last week. He became the two-thousandth U.S. soldier to die in the war.

The Senate's top Democrat, Senator Harry Reid of Nevada, offered his own tribute to the U.S. troops who lost their lives in the Iraq war. "We all have been touched by the deaths of these two-thousand, in one way or the other," he said.

Just hours before the Pentagon's announcement, President Bush said the war in Iraq would require more sacrifice, saying in a speech, no one should underestimate the difficulties ahead. He also took issue with critics who are calling for a withdrawal of U.S. forces from Iraq.

One of those critics, Senator Russ Feingold, a Wisconsin Democrat, has called for U.S. troops to leave Iraq at the end of this year. He spoke shortly after President Bush delivered his speech.

"I think it is becoming an increasingly clear that we have created a breeding ground for terrorism in Iraq, and that the apparent indefinite presence of tens of thousands of U.S. troops is often fueling, fueling not dampening the insurgency in that country," senator Feingold said.

Another Democrat, Senator Patrick Leahy of Vermont, criticized President Bush's call to stay the course in Iraq. Senator Leahy urged Mr. Bush to consult with Congress on a plan to begin withdrawing U.S. troops from densely populated areas of Iraq once a new Iraqi government is in place.

Senator John McCain, an Arizona Republican and a former prisoner of war in Vietnam, chastised his Democratic colleagues who used the grim death toll milestone to criticize Bush administration policy in Iraq.

"I would hope that the sacrifice made by young Americans would not be used for political reasons. There are plenty of ways to criticize the conduct of the war if you want to, I would hope that the loss of a brave, young American would not be a rationale for doing so," Senator Mccain said.

The Senate debate comes amid waning public support for the war in Iraq.