U.S. President George W. Bush on Monday called deadly bombings in London an attack against the civilized world and vowed "we will not yield." Drawing parallels among fighting terrorism, World War Two and the Cold War, Bush declared: "Like fascism and communism before, the hateful ideologies that use terror will be defeated by the unstoppable power of freedom and democracy." "The only way the terrorists can win is if we lose our nerve. This is not going to happen on my watch," he said to applause from agents, Marines and emergency workers at an FBI facility south of Washington, according to Reuters. Bush, who was with British Prime Minister Tony Blair at a Group of Eight summit in Scotland when the attacks occurred in London last Thursday, said it was unclear who was responsible for the bombings that killed more than 50 people, but noted that "we have damaged the al Qaeda network across the world." One American citizen is missing and presumed killed in the attacks, U.S. State Department spokesman Tom Casey said. He declined to elaborate to protect the privacy of the victim's family. "The attack in London was an attack on the civilized world, and the civilized world is united in its resolve," Bush said. "We will not yield, we will defend our freedom." Bush expressed U.S. solidarity with the British people. --More 2245 Local Time 1945 GMT