In his radio speech Saturday, Mr. Bush said that if the United States were to pull its troops out of Iraq before winning there, future generations would face a Middle East dominated by terrorist states and radical dictators armed with nuclear weapons.
He said world security depends on supporting Iraq's fledgling democracy and defeating the insurgency there.
The president's radio address echoed themes Mr. Bush stressed earlier this week in a speech to U.S. war veterans. This new series of speeches will continue through the anniversary of the September 11 terrorist attacks and will culminate at the United Nations on September 19.
His speeches are aimed at bolstering public support for the administration's policies ahead of the November congressional elections.
Opinion polls indicate the president has an approval rate in the 30 percent range, with the Iraq war being one reason for that low number.
On Friday, in a quarterly report to Congress, the U.S. Defense Department said insurgent and sectarian attacks in Iraq are becoming more frequent. The report said current conditions in Iraq could lead to civil war.
Some information for this report was provided by AFP, AP and Reuters.