The first bomb exploded in London Thursday as President Bush and British Prime Minister Tony Blair were briefing reporters at this golf resort about their often contrasting approaches to African poverty and global warming. Within an hour, word arrived of the carnage in the British capital and the two leaders switched to their familiar roles as partners in war.

Bush and Blair later huddled with other government heads attending a world summit here to map out a response to the most recent act of what the prime minister called "barbaric" terrorism.

Bush retired to a suite in the resort and consulted his national security officials by secure video conference link, U.S. officials said. Blair, meanwhile, was briefed on the conflicting reports of death, injury and chaos in London, where bombs had devastated three subway trains and a red double-decker bus, killing at least 37 people.

Shortly after noon, a visibly shaken Blair, with fellow world leaders, including Bush, standing behind him, offered an emotional warning to the killers on TV. "Whatever they do," Blair said, "it is our determination that they will never succeed in destroying what we hold dear in this country and in other civilized nations throughout the world."

For all their differences on issues such as poverty, the environment and trade, Bush and Blair share a seemingly unshakable bond over terrorism that began with the attacks of Sept. 11, 2001. Both men adhere to a strict ideological and moral belief in the need to fight terrorists at home and abroad. That conviction has defined their leadership and stirred ardent opposition. The events of Thursday appeared to renew their bond.

After delivering his statement, Blair boarded a helicopter and flew to London. The summit shifted from a discussion of the causes of poverty and global warming to finding those responsible for an attack that resembled the 2004 bombings of four rush-hour commuter trains in Madrid that killed 190 people.

As Blair's helicopter took off, Bush walked away from a meeting on the resort's back lawn to assume the role of loyal and forceful ally, just as Blair had after the September 11 attacks.

"The contrast between what we've seen on the TV screens here, what's taken place in London and what's taking place here is incredibly vivid to me," Bush told a small group of U.S. reporters.

"On the one hand, we have people here who are working to alleviate poverty, to help rid the world of the pandemic of AIDS, working on ways to have a clean environment. And on the other hand, you've got people killing innocent people.

"And the contrast couldn't be clearer between the intentions and the hearts of those of us who care deeply about human rights and human liberty, and those who kill -- those who have got such evil in their heart that they will take the lives of innocent folks."

Afterward, the White House announced that all of Bush's other media appearances for the day were postponed. Bush did not alter his plans to stay here until Friday afternoon. First lady Laura Bush was also scheduled to leave Friday for Africa.

The leaders were intent on sticking to the summit's agenda. Most meetings took place as scheduled despite the bombings, but the release of joint statements on global warming and other issues was delayed.

At about 2:30 p.m., Stephen J. Hadley, the president's national security adviser, conveyed to Bush a recommendation from U.S. homeland security officials to raise the terror alert for transit systems back home, which Bush signed off on. Bush attended the remaining meetings, including an evening reception, according to White House press secretary Scott McClellan.

During the day, other world leaders put aside differences with Britain to show support following the bombings. French President Jacques Chirac, who has sparred bitterly with Blair over Iraq and more recently over France's losing bid to host the 2012 Olympics, told the prime minister his nation stood with the British people. "He expressed the total solidarity of France and the French people," Chirac's spokesman told the Reuters news agency.

Russian President Vladimir Putin, a critic of the Iraq campaign, said in a statement that "what happened today again testifies to the fact that all of us are doing too little to unite our forces effectively in the struggle against terrorism." Before the bombings upended the agenda, Putin had considered calling for a strict timeline for pulling foreign troops out of Iraq.

Speaking Thursday evening from London before he returned to Gleneagles, Blair echoed the post-Sept. 11 words of Bush. "We will show through our spirit and dignity that our values will long outlast theirs," Blair said. "The purpose of terrorism is just that -- to terrorize people, and we will not be terrorized. This is a very sad day for the British people. But we will hold true to the British way of life."

President Bush stands behind Tony Blair as the British prime minister makes a statement about the London bombings during a world summit at the Gleneagles resort in Scotland.