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.

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.

"In late March of 2008 ... both coalition and Iraqi security force casualties are down significantly from about May of '07. Iraqi civilian casualties has also been on a downward trend since December of '06.