President Bush and the leaders of seven other major industrialized nations pledged Friday to double the amount of aid for Africa in five years and substantially raise it for other poor countries, capping a summit conducted in what British Prime Minister Tony Blair called the "shadow of terrorism."

Blair failed to convince Bush to embrace mandatory caps on greenhouse gas emissions, and the summit issued instead a watered-down pledge to take other steps to combat global warming, such as the development of new technologies. World leaders will meet Nov. 1 to discuss new ways to reduce the pollutants blamed for slowly rising temperatures, Blair announced.

The aid accord was a victory for Blair, the summit's host, who has made helping Africa a priority of his government. Some activists complained that the plan to increase aid for Africa to $50 billion a year by 2010 was too slow, but Blair won praise from the Irish rock star Bono and other celebrities who staged concerts in 10 cities around the world last weekend to pressure summit participants on behalf of the world's poor.

The summit, which brought together leaders of the Group of Eight countries and other heads of government, ended shortly before noon Friday so that Blair could return to London, where bomb attacks killed at least 49 people Thursday.

Before leaving, Blair declared that the "hope" and "humanity" behind the aid deal sent a powerful and timely message. "The clear signal we have sent on Africa," he said, "stands in stark contrast to the politics of terror."

The attacks created a spirit of solidarity among the G-8 leaders that encouraged compromise on aid for Africa and on how to promote peace in the Middle East.

The group, which is made up of the United States, Britain, Canada, France, Germany, Italy, Japan and Russia promised to spend up to $3 billion a year for the next three years to help build an independent Palestinian state.

For completing the Africa package, they were thanked by Nigerian President Olusegun Obasanjo, who attended Friday. He hailed "their resolve not to be diverted by these terrorist acts."

The leaders portrayed their pledges of new aid as both humanitarian and anti-terrorist, because the assistance would help prevent the rise of groups like al Qaeda in impoverished nations. They promised that by 2010, overall aid to poor nations, now about $80 billion a year, would rise by $50 billion a year, with half of the increase going to Africa.

Although much of that increase consisted of pledges made in earlier initiatives, it got an unexpected boost from Japanese Prime Minister Junichiro Koizumi, who promised $10 billion in new funding over five years.

In addition, the leaders endorsed a deal struck by their finance ministers last month to forgive the debts owed to the International Monetary Fund and the World Bank by 18 poor countries, 14 of them African.

They also pledged to set a date for ending the billions in subsidies for agricultural exports, reiterating a commitment previously made at World Trade Organization meetings. Such subsidies are widely blamed for lowering the prices of products sold by poor countries on world markets.

"It is in the nature of politics that you do not achieve absolutely everything you want to achieve," said Blair, who acknowledged that he had wanted the G-8 to set a date for ending farm subsidies rather than just promising to do so. "We do not simply by this communique make poverty history," he said. "But we do show how it can be done. And we do signify the political will to do it."

Blair noted that the rich countries now had to ensure that the money pledged was actually disbursed, and that Africans had to use the funds wisely: "In the end it is only vibrant African leadership, capable of giving good governance to its people, that will ultimately make the difference."

Some aid advocates criticized the accords as too modest. "If the $50 billion increase had kicked in immediately, it could have lifted 300 million people out of poverty in the next five years," said Jo Leadbeater, of Oxfam. Kumi Naidoo of Global Call to Action Against Poverty agreed: "The promise to deliver by 2010 is like waiting five years before responding to the tsunami."

But such criticism was rejected by Bono and fellow Irish activist musician, Bob Geldof, the organizer of the "Live 8" concerts.

"Doubling aid to Africa has not been easy. I'm very proud to report that these figures are extremely meaningful," Bono told reporters. Thanks to additional funding for malaria prevention, he said, "six hundred thousand Africans, mostly children, will remember this summit at Gleneagles -- because they'll be around to remember it."

"Today, celebrate," Geldof said, noting that as many as 8 million lives may be saved by the G-8's additional commitment to provide funding for treating all HIV/AIDS victims by 2010.

The U.S. share of the increases promised Friday was about $4.5 billion. Although the Bush administration has also pledged to double aid to Africa, most of that money represents commitments previously made.

Washington did not add new money at Gleneagles. The U.S. contribution comes to about 20 percent of the pledged increase in aid for Africa and a smaller proportion of total aid for the continent.

Global warming emerged as the most contentious issue of the three-day talks. Bush made it clear before, during and after the summit that the United States was opposed to the caps on greenhouse gas emissions contained in the Kyoto Protocol of 1997, which was ratified by all G-8 countries except the United States.

That forced Blair and others to fight instead for agreement that the earth is warming, humans are partly to blame and that the United States must cooperate with the rest of the world to reduce the pollution believed to contribute to global warming.

While the final climate statement was much more tentative than earlier drafts, American and European officials hailed the fact the leaders agreed on the need for action. James L. Connaughton, Bush's top environment adviser, said the joint communique showed that the major industrialized nations had "agreed to the basic portfolio of what we need to do . . . . We have found a way to strike common ground."

A British official who spoke on condition of anonymity said that as recently as June the Europeans despaired of reaching an agreement with the Americans. "We think we advanced our objective of getting the Americans and the Europeans back on the same page in terms of climate," the official said, adding that coming months would show whether cuts in gas emissions actually occurred .

Nicole St. Clair, a spokeswoman for the Natural Resources Defense Council, described the communique as "a stalemate" on climate change. But she said it established an important baseline for future negotiations. "It's clear that the administration can no longer turn back the clock on the science or slow the desire for real action to stop the pollution," she said.

Staff writer Juliet Eilperin in Washington contributed to this report.

President Bush and Nigerian President Olusegun Obasanjo at the summit, where leaders agreed to increase aid to poor nations by $50 billion a year.