WASHINGTON — As the U.S. death toll in Iraq climbed to 4,000, the White House said on Monday that President Bush spends time every day thinking about those who have lost their lives in battle.

"The president is committed to successfully completing the mission, which is one of the main requests he hears from families of the fallen," White House press secretary Dana Perino said.

With the war entering its sixth year, Bush makes the argument that defeating extremists in Iraq makes it less likely that Americans will encounter enemies at home. Iraq has taken a heavy toll on his presidency, contributing to Bush's low poll ratings.

Commenting on the 4,000 deaths, Perino said, "President Bush believes that every life is precious, and he spends time every day thinking about those who've lost their lives on the battlefield. He grieves for the families who have lost loved ones, and he is constantly concerned about their well-being."

"The president has said the hardest thing a commander in chief will do is send young men and women into combat, and he's grieved for every lost American life, from the very first several years ago to those lost today," the press secretary said.

Perino said that the security gains of the past year have been important to stabilizing Iraq. Bush is to receive briefings Monday at the State Department and on Wednesday at the Pentagon "on what actions his advisers recommend for cementing those gains and taking action that will lay the foundation for further additional troop draw-downs," she said.

"The president is extremely proud of the courageous and honorable service displayed by our military and the civilians who are helping the Iraqis rebuild their country to establish democracy in Iraq that will improve the lives of the Iraqis, ensure an ally in the war on terror in the heart of the Middle East, and will help protect our own national security," Perino said.

The U.S. has about 158,000 troops in Iraq. That number is expected to drop to 140,000 by summer in draw-downs meant to erase all but about 8,000 troops from last year's increase.