FACTBOX: U.S. leaders mark 4,000 American dead in Iraq

(Reuters) - U.S. leaders on Monday marked the passing of a new milestone in Iraq after the number of U.S. service members killed in the war reached 4,000.

Following are comments from presidential candidates, Bush administration officials and lawmakers on the war in Iraq.

PRESIDENT GEORGE W. BUSH

"One day people will look back at this moment in history and say 'thank God there were courageous people willing to serve' because they laid the foundation for peace for generations to come. ... I have vowed in the past and I will vow so long as I'm president to make sure that those lives were not lost in vain."

VICE PRESIDENT DICK CHENEY

"It places a special burden, obviously, on the families. We recognize, I think -- it's a reminder of the extent to which we're blessed with families who have sacrificed as they have. The President carries the biggest burden, obviously; he's the one who has to make the decision to commit young Americans. But we are fortunate to have the group of men and women, the all-volunteer force, who voluntarily put on the uniform and go in harm's way for the rest of us."

SEN. JOHN MCCAIN, PRESUMPTIVE REPUBLICAN PRESIDENTIAL

NOMINEE

"My thoughts and my prayers go out to them (the families of the dead) every day, not just on the day that 4,000 brave young Americans are sacrificed."

"I wear a bracelet on my hand not only a symbol of the sacrifice that a brave young man named Matthew Stanley made, but that of 4,000 other brave young Americans who have served and sacrificed."

DANA PERINO, WHITE HOUSE SPOKESWOMAN

"It's a sober moment, and one that all of us can focus on in terms of the number of 4,000.

"The president feels each and every one of the deaths very strongly and he grieves for their families ... He obviously is grieved by the moment but he mourns the loss of every single life.

"One of the things that he hears from families of the fallen is that they want him to lead the country to complete the mission and he is committed to doing that ... He wants them to know that their sacrifices will not be in vain."

BRYAN WHITMAN, PENTAGON SPOKESMAN

"Every single loss of a soldier, sailor, airman and Marine is keenly felt by us in the (Defense) Department, by military commanders, by families, friends.