President Bush says there can be no appeasement of terrorists, and warns they seek a radical Islamic empire. Mr. Bush says terrorists have made Iraq their central front and the United States will not turn away.
The president says the war on terrorism will not be easy and there will be sacrifice. But he says victory is essential.
"Our goal is to defeat the terrorists and their allies at the heart of their power, and so we will defeat the enemy in Iraq," he said.
In an address in Washington to a group that promotes democratic ideals around the world, the National Endowment for Democracy, the president took on critics of his Iraq policy.
To those who say the U.S. presence has only provoked more violence and the needless deaths of many Iraqi civilians, Mr. Bush had an answer.
"Some observers look at the job ahead and adopt a self defeating pessimism. It is not justified," he said. "With every random bombing, and every funeral of a child, it becomes more clear that the extremists are not patriots or resistance fighters they are murderers at war with the Iraqi people themselves."
President Bush linked the terrorists who have staged attacks in cities around the world, from New York to Bali, London to Sharm al Sheikh, to tyrants of the past. He spoke of those responsible for Nazi atrocities, the gulags of the former Soviet Union, Cambodia's killing fields, and China's Cultural Revolution.
The president said the radicals waging today's terrorist attacks are cowards who kill innocents in preparation for a future of oppression. He said they seek to enslave whole nations and intimidate the world.
"Evil men obsessed with ambition and unburdened by conscience must be taken very seriously and we must stop them before their crimes can multiply," added Mr. Bush.
The comments come at a time of slipping support for the president's Iraq policies in public opinion polls, as well as heightened criticism on Capitol Hill.
With the referendum on Iraq's new constitution coming in less than two weeks, Mr. Bush is redoubling efforts to lay out his case for continued involvement in Iraq. Aides say this address was designed to explain the stakes involved to the American people, and to warn them of possible sacrifices ahead in the cause of freedom.
The president pointed to some signs of progress, most notably the ongoing political process in Iraq and the training of the Iraqi military. He also spoke of efforts to thwart terrorist attacks before they occur, noting that ten al-Qaida plots have been disrupted since September 11 2001, including three in the United States.