"They are mistaken," Mr. Bush said of the terrorists. "America will not retreat in the face of terrorists and murderers."
Mr. Bush came to the FBI training academy in Virginia to deliver a progress report on the war on terror. The White House said the address was planned before last week's bombings in London, but the deadly attacks give his remarks even more significance.
"There is only one course of action," the president said. "We will continue to take this fight to the enemy and we will fight until this enemy is defeated."
He spoke before an audience of 1,000 FBI officials, Marines and emergency first-responders. After his remarks, Mr. Bush went to shake hands with Attorney General Alberto Gonzales, who had been sitting in the front row. The handshake prompted a flurry of picture-taking since Gonzales is rumored as a candidate for the Supreme Court.
"Now why are you taking photos of us?" Bush playfully asked photographers. "One way to get in the paper is to stand next to Gonzales."
Mr. Bush's war against the terrorists is a major reason he won re-election last year: Americans came out of the voting booth saying they thought he would do a better job of protecting them from another attack.
It also remains his strength. Americans responded to an AP-Ipsos poll conducted last month by giving the president higher job approval ratings on terrorism than on his handling of the Iraq war, Social Security or other domestic issues.
Yet his approval numbers have slipped in recent months leading up to Monday's speech at Quantico.
"There will be tough fighting ahead," Mr. Bush cautioned. "There will be difficult moments along the path to victory. The terrorists know they can't defeat us on the battlefield. The only way the terrorists can win is if we lose our nerve. This isn't going to happen on my watch."
The president spoke at Quantico assaid it seems probable the London attacks were carried out by Islamic extremist terrorists.
"We don't know who committed the attacks in London," he said. "But we do know that terrorists celebrate the suffering of the innocent. We do know that terrorists murder in the name of a totalitarian ideology that hates freedom, rejects tolerance and despises all dissent.
"Their aim, the aim of the terrorists, is to remake the Middle East in their own grim image of tyranny and oppression by toppling governments, by exporting terror, by forcing free nations to retreat and withdraw," Mr. Bush said.
The London bombings fresh in the minds of Americans, Mr. Bush called on Congress to extend provisions of the Patriot Act that are set to expire at year's end.
The Patriot Act, Congress' swift reaction to the Sept. 11 attacks, allowed expanded surveillance of terror suspects, increased use of material witness warrants to hold suspects incommunicado and permitted secret proceedings in immigration cases. Now, more than a dozen provisions are set to expire later this year. Congress has begun working on renewing them amid fresh criticism — from members of both parties — that the law undermines basic freedoms.
"The terrorist threats against us will not expire at the end of this year, and neither should the protections of the Patriot Act," he said.
"We know that there's no such thing as perfect security and that in a free and open society it is impossible to protect against every threat," the president said.
"As we saw in London last week, the terrorists need to be right only once," he said. "Free nations need to be right 100 percent of the time."