Bush, facing waning support for the war, argued that Iraq is making progress by approving a new constitution and that Iraqi troops are increasingly playing a larger role in defending against the insurgency.
"Each loss of life is heartbreaking, and the best way to honour the sacrifice of our fallen troops is to complete the mission and lay the foundation of peace by spreading freedom," Bush said, his voice breaking with emotion as he spoke to a luncheon of military wives at Bolling Air Force Base in Washington.
In a lengthy speech, Bush said those calling for a US withdrawal from Iraq were refuted by a simple question, whether America and other nations would be more or less safe if Iraqi insurgency leader Abu Musab al-Zarqawi and al Qaeda leader Osama bin Laden were in control of Iraq.
Bush's remarks were aimed at addressing criticism expected when the US death toll in Iraq reaches the 2,000 milestone. It stood at 1,999 on Tuesday.
"This war will require more sacrifice, more time and more resolve," he said. "The terrorists are as brutal an enemy as we have ever faced."