In a radio address on the eve of the third anniversary of the US-led invasion of Iraq on Saturday, George Bush urged Americans growing increasingly impatient with the war to resist a temptation to retreat, even as he acknowledged the prospect of more bloodshed.
"I urge them to continue their work to put aside their differences, to reach out across political, religious and sectarian lines," he said of Iraqi politicians, still deadlocked over who will lead a new government three months after polls.
Bush insisted that despite "horrific" images in Iraq, progress was being made on the political and military fronts.
However, he warned the American public: "More fighting and sacrifice will be required to achieve this victory, and for some, the temptation to retreat and abandon our commitments is strong."
Pessimism over Iraq has helped drag Bush's approval ratings to about 35% in recent polls, the lowest level of his presidency.
"These past three years have tested our resolve. We've seen hard days and setbacks," he said, but added that his administration was "fixing what has not worked".
Washington says a government of national unity embracing Sunnis, Kurds and Shia is the best hope of stabilising Iraq and allow it to begin pulling out its 133,000 troops.
While Iraqi leaders wrestle over a new government, Iraq continues to be gripped by sectarian bloodshed, sparking fears of civil war.
"These past three years have tested our resolve. We've seen hard days and setbacks"
More than 100 bodies, victims of apparent sectarian killings, were found in Baghdad alone this week, complicating efforts to form a government.
Police said 16 bodies were found dumped around the capital on Saturday, all apparent victims of sectarian bloodshed.
More than 2300 US troops have died in the war.
A US troop withdrawal, Washington says, hinges on whether Iraq's army, disbanded after the war by US authorities but now being rebuilt, can improve its capability.