TOYAKO, Japan — China, India, and other energy-guzzling developing nations yesterday rejected key elements of a global warming strategy embraced by President Bush and leaders of wealthy nations. And the U.N’s top climate official dismissed the G-8 goals as insignificant.

The sharp criticism emerged at the close of a summit here of the Group of Eight industrial powers that was dominated by the issue of how to address the warming Earth. The G-8 leaders invited their counterparts from fast-growing, pollution-emitting nations to sideline talks on the topic, but the session merely showcased a widening rift over the best approach.

It was the final G-8 summit of Mr. Bush’s presidency and he said “significant progress” had been made on fighting global warming when the leaders agreed to slash greenhouse gas emissions in half by 2050 and to insist that developing nations be part of any new international agreement.

“In order to address climate change, all major economies must be at the table, and that’s what took place,” Mr. Bush said before boarding Air Force One to return to Washington.

The “major economies” are the world’s 16 largest-emitting nations, accounting for 80% of the world’s air pollution. The expanded meeting that included all of them was the first time their leaders had sat down together for climate discussions.

But it ended with only a vague reference in their final declaration to a long-term goal for reducing global emissions and a pledge for rich and poor countries to work together. Only a few of the emerging powers — Indonesia, Australia, and South Korea — agreed to back the 50% by 2050 reduction target.

The five main developing nations — China, India, Brazil, Mexico, and South Africa, who together represent 42% of the world’s population — issued a statement explaining their split with the G-8 over its emissions-reduction goals. They said they rejected the notion that all should share in the 50% target, since it is wealthier countries that have created most of the environmental damage up to now.