"RUSUTSU, Japan, July 9-- The leaders of the countries most responsible for greenhouse gas emissions pledged Wednesday to combat global warming, but developing countries such as China and India continued to balk at the approach favored by the United States.

The 16 countries, along with the heads of the European Commission, the United Nations and the World Bank, met in an unusual meeting brokered by President Bush during the last day of the Group of Eight summit on the Japanese island of Hokkaido. It was aimed at trying to come together behind a new treaty to replace the Kyoto Protocol, the 1999 pact aimed at curbing carbon emissions.

On Tuesday, Bush agreed for the first time to join other major industrialized countries in setting a goal to reduce emissions. He and other leaders of the G-8 countries forged a joint communique that declares the countries will "consider and adopt" reductions of at least 50 percent as part of a new U.N. treaty to be negotiated in Copenhagen at the end of 2009. The step was the most recent sign of a gradual shift in Bush's approach to combating global warming.

The G-8 leaders also said they expect such developing countries as China and India, which are also major greenhouse-gas polluters, to promise "meaningful" actions to reduce emissions. That has been a key objective for Bush but presents an obstacle: Those countries have said repeatedly that the industrialized world, having caused most of the problem historically, must bear the greatest burden, while they need more relaxed rules to pursue economic development.

There is little sign that the key differences have been resolved. The statement released Wednesday by the participants in the meeting included no reference to specific targets. The "big five" developing countries -- China, India, Brazil, South Africa and Mexico -- met themselves this week and called for much steeper reductions than the G-8. While they said they would undertake their own efforts to address global warming, they said that developed countries must "take the lead" on the issue.

"There are definitely two different views here," said Marthinus van Schalkwyk, South Africa's environmental minister.

Still, the meeting between developing and developed countries Wednesday was described as cordial and constructive by U.S. officials, and Bush told reporters here that the parties made "significant progress."

"In order to address climate change, all major economies must be at the table," Bush said. "And that's what took place today. The G-8 expressed our desire to have . . . a significant reduction in greenhouse gases by 2050. We made it clear and the other nations agreed that they must also participate in an ambitious goal, with interim goals and interim plans to enable the world to successfully address climate change."

Bush spoke just before leaving for Washington after four days of G-8 meetings, which included bilateral sessions with key leaders gathered here. On Wednesday, Bush had one-on-one meetings with the leaders of China, India, South Korea and Brazil. He told Chinese President Hu Jintao that he looked forward to attending the Olympics in Beijing next month, while speaking with Indian Prime Minister Manmohan Singh of his continuing desire to achieve a deal to sell India nuclear technology.

Bush also hailed the progress at the G-8 not only on climate change, but also in forging plans for a successful Doha trade round, confronting disease in Africa and addressing the high cost of food and oil. "We accomplished a lot," he said. "By protecting our environment and resisting protectionism and fighting disease and promoting development and improving the daily life for millions around the world, we serve both our interests as Americans, and we serve the interest of the world."

The language of the communique Wednesday outlined different responsibilities of the developed and developing world towards combating global warming.

"[Developed] major economies will implement, consistent with international obligations, economy-wide mid-term goals and take corresponding actions in order to achieve absolute emission reductions," the document said. "At the same time," it said, developing countries like China agreed to "deviate from business as usual" in trying to slow or reduce emissions.

The communique's language drew the disapproval of many environmental groups, which said the targets were weak or ambiguous. They accused the summit leaders of not addressing fundamental differences among themselves on matters such as speed and method, resulting in a plan with little real meaning.

The G-8 leaders "have failed the world again," Daniel Mittler, Greenpeace International's climate expert, said in a statement. "While the Arctic is melting, the G-8 are postponing action. Instead of climate protection, the world got nothing but flowery words."

The environmental minister of South Africa, one of several developing countries whose support on climate change is being courted, called the long-term goal an "empty slogan" and took a veiled shot at the United States. "We know very well that there are many countries in the G-8 grouping that share our ambitious expectations, and therefore it is regrettable that the lowest common denominator in the G-8 determined the level of ambition," said Schalkwyk.

Other people who follow the issue closely, including Europeans who have criticized Bush's approach, saw significance in the move by a president who came to office questioning the science and impact of climate change and, until now, had refused to commit to any numerical goal.

At the last G-8 summit, in Germany a year ago, the United States alone refused to adopt the 50 percent target. While the White House has since said Bush would accept binding midterm targets as long as the developing world went along, European officials called it important that he agreed to place the language in the G-8 communique.

"I think that President Bush has moved considerably over the past one to two years," said Jos Delbeke, a top environmental official at the European Commission, the executive arm of the European Union.

Michael A. Levi, director of the program on energy security and climate change at the Council on Foreign Relations, said in an interview that agreeing to the long-term goal is a "very important" step toward addressing a climate trend that many experts say is already causing environmental dislocations in parts of the world.

Early in his administration, Bush moved to keep the United States out of the Kyoto Protocol, straining relations with the European Union and Japan. His subsequent shift appears to have stemmed from firmer scientific findings, pressure from allies and Democrats in Congress, and the conclusion reached by senior White House officials that the president could not afford to be seen as absent from the debate.

White House aides say Bush genuinely wants a plan but thinks the debate to date has focused too often on unrealistic aims rather than specifics, such as new efficiency standards or helping developing countries create clean technologies. Sens. John McCain and Barack Obama have both indicated an interest in steeper emissions reductions than Bush wants, but Levi said U.S. allies, particularly Japan, have been reluctant to box in the next president by negotiating a deal without Bush and presenting it to his successor as a fait accompli.

"This sets a frame for negotiations that the next president, regardless of who it is, will be happy to work within," Levi said.

The global warming statement came on a busy day at the G-8 summit, taking place at a highly secured resort on the scenic island of Hokkaido. Bush and the leaders of Japan, Russia, Canada, France, Germany, Britain and Italy weighed in collectively on a panoply of world problems. They promised new steps to confront the escalating cost of food around the globe and expressed concern about the world economic slowdown.

The leaders pledged that $60 billion promised earlier to fight disease in Africa would be spent over five years and agreed, at the behest of the United States, to release reports detailing whether G-8 countries are meeting their aid commitments. Advocacy groups complained that the industrialized countries would not spend the money fast enough.

A hot subject here has been Zimbabwe, with Bush and British Prime Minister Gordon Brown promoting a tough new round of sanctions aimed at dislodging President Robert Mugabe, whose campaign of intimidation led many countries to reject his recent reelection. The G-8 communique questioned the legitimacy of the Mugabe government and promised possible "financial and other measures against those individuals responsible for violence."

The statement did not use the word "sanctions," an apparent nod to African countries and Russia, which have question the utility of sanctions. At U.N. headquarters in New York on Tuesday, Russian Ambassador Vitaly I. Churkin suggested that his country may veto any Security Council sanctions, on the grounds that Zimbabwe's crisis does not present a threat to international security.

But it was global warming that attracted the most attention here, in large part as a test of how far Bush would go on the issue before he leaves office in less than seven months.

The summit leaders left unaddressed several key issues, such as the baseline for calculating a 50 percent reduction in greenhouse-gas emissions. Japanese Prime Minister Yasuo Fukuda, the host of the meeting, told reporters the baseline will be current levels of emissions, but European officials said that the matter must still be negotiated and that they prefer the baseline to be 1990 levels, necessitating deeper emissions cuts.

The uncertainty angered environmental groups. Alden Meyer, who is tracking the climate change issue here for the Union of Concerned Scientists, described the statement as a "missed opportunity," and noted that the United States did not budge from its position that its midterm goal for 2025 will be to halt the growth of greenhouse-gas emissions, not cut them.

In general, European countries favor ambitious midterm and long-term emissions-reduction targets. The United States, joined to varying degrees by Canada and Russia, has been wary of setting what it calls unrealistic targets.

One reason Bush cited for staying out of the Kyoto Protocol was that it exempted developing countries from emissions cuts. Daniel M. Price, one of the White House negotiators at this year's G-8 summit, said the president is making progress in bringing those countries into a new climate change treaty.

"The G-8 declaration is a significant contribution both to the U.N. negotiations, as well as to the major economies process," Price said. "Much work lies ahead, but right now we've got the right countries around the table, not only around the G-8 table but, more importantly, around the broader major economies table."" (Michael Abramowitz, The Washington Post, July 15, 2008)

Staff writer Colum Lynch at the United Nations contributed to this report.