GLENEAGLES, Scotland — The first bomb exploded in London yesterday as President Bush and British Prime Minister Tony Blair were briefing reporters 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 latest act of what the prime minister later called "barbaric" terrorism.

Bush retired to a suite in the resort and consulted his national security officials by secure video-conference link, officials said. Blair, meanwhile, was briefed on the conflicting reports of death, injury and chaos in London.

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. Yesterday's events appeared to renew their bond.

After delivering his statement, Blair flew to London, with plans to return last night. 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 9/11.

"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 said.

"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."

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 until today.

The leaders' joint statement, which was obtained by The Washington Post, says they have agreed to take immediate steps to curb global warming, though they will not set concrete heat-trapping gas reductions or specify how much money they will spend on the effort.

During the day, other world leaders put aside differences with Britain to show support after the bombings. French President Jacques Chirac, who has sparred with Blair over Iraq and France's losing quest 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 Reuters.

Russian President Vladimir Putin, a critic of the Iraq campaign, said 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 yesterday from London before he returned to Gleneagles, Blair echoed the post-9/11 words of Bush.

"The purpose of terrorism is just that — to terrorize people, and we will not be terrorized," Blair said. "This is a very sad day for the British people. But we will hold true to the British way of life."

Blair has long shown a sure rhetorical touch in times of crisis. When Diana, Princess of Wales, died in 1997, the newly elected Blair delivered a memorable speech dubbing her the "people's princess."

Hours after the Sept. 11 attacks, Blair vowed that Britain would "stand shoulder to shoulder with our American friends in this hour of tragedy, and we, like them, will not rest until this evil is driven from our world."

Blair has a talent for bouncing back from adversity. Just two months ago, he seemed to be a spent political force after British voters returned him to office for a third term but with a sharply reduced majority in Parliament.

But the chance to host the G-8 summit and his recent assumption of the rotating European Union presidency as the 25-nation bloc struggles for a direction appear to have reinvigorated him. And Blair's poised performance yesterday once again proved he is a leader who thrives in times of crisis.

In his address, Blair harkened back to the "Blitz spirit" that saw Londoners through the dark days of Nazi bombing during World War II — and, by association, to Winston Churchill, the wartime leader whose determined, moving speeches helped steel the national resolve.

"There will, of course, now be the most intense police and security service action to make sure that we bring those responsible to justice," Blair said. "I would also pay tribute to the stoicism and resilience of the people of London who have responded in a way typical of them."

He said Britain would show "by our spirit and dignity" that "our values will long outlast" the terrorists.