U.S. forces, he added, are "plenty tough" to deal with any security threats.
The president made his comments as he spoke to reporters at the White House, following an announcement about his program to combat AIDS in Africa and the Caribbean.(Full story)
They echoed comments he made Tuesday, when he appeared to address growing concerns about U.S. military deaths in Iraq and the continued U.S. military presence there. In March, U.S. forces led an invasion of Iraq to topple the government of Saddam Hussein, whom the United States and allies said was developing weapons of mass destruction.
But Bush's tough talk was criticized by Democratic presidential candidate Dick Gephardt who said the president should stop with the "phony, macho rhetoric."
"I have a message for the president," Gephardt said in a statement. "We should be focused on a long-term security plan that reduces the danger to our military personnel."
"We need a clear plan to bring stability to Iraq and an honest discussion with the American people on the cost of that endeavor," Gephardt's statement continued. "We need a serious attempt to develop a postwar plan for Iraq and not more shoot-from-the-hip one-liners."
Since May 1 -- when Bush declared an end to major combat in Iraq -- there have been more than two dozen "hostile" U.S. military deaths in Iraq, according to the Pentagon.
Bush said on Tuesday that rebuilding Iraq, following a U.S.-led invasion there, will be a "massive and long-term undertaking," one that he suggested would require further sacrifice.
Some lawmakers, however, have begun to question how long the United States should remain in Iraq.
For example, Rep. Curt Weldon, R-Pennsylvania, on Tuesday called for troops to leave Iraq as soon as possible. Speaking to a group of business executives in Washington, Weldon, a strong supporter of the war in Iraq, said one of Congress' "greatest concerns is that our government not get bogged down with our military for the long term."
He added, "Yes, we want to guarantee stability in that country," but steps should be taken so that "as soon as possible we can bring our troops back home."
The administration has not provided a specific timeline for when the United States will pull troops out of Iraq.
"We're not leaving until we accomplish the task," Bush said Wednesday.
--CNN Senior White House Correspondent John King contributed to this report.
