The White House is closely monitoring developments in London following new attacks on that city's transit system.
President Bush says terrorists are trying to shake the will of the free world. He says they will fail.
"They don't understand that when it comes to the defense of universal freedoms, this country won't be frightened," he said.
The comments came in a speech at the Washington headquarters of the Organization of American States a few hours after explosions were reported in three London subway stations and a city bus.
Mr. Bush did not refer to these latest incidents directly. Instead, he inserted comments on the war on terrorism in a planned address on a pending Central America trade pact.
The words were familiar. But they were delivered with an extra emphasis. His tone was one of determination in the face of the terrorist threat.
"This is a war against killers, cold blooded killers who embrace an ideology of hatred," he said. "Their vision of the world is the opposite of our vision of the world. We believe in human rights, human dignity, minority rights and religious rights. We believe in universal freedoms."
The president got briefings from top aides on the London attacks both before and after the speech. White House Spokesman Scott McClellan said he would continue to monitor developments.
At the State Department, Spokesman Adam Ereli said America stands with the British people in dealing with this tragedy.
"As you would expect, we stand with our British friends and allies in response to this act as we have in response to the many challenges we face together brought by those who seek to undermine our commonly held values and common way of life," he said.
Mr. Ereli said the U.S. embassy in London has been temporarily closed to the public except for emergencies. Here at the White House, officials say there are no plans to increase the terrorism alert level in the United States. However, the heightened state of alert put in place on the nation's transit systems after the London bombings on July 7 will remain in effect.