"The US will be actively involved, if not taking the lead, in a post-Kyoto framework, a post-Kyoto deal," Bush said after talks with British Prime Minister Tony Blair, referring to the UN-backed treaty on cutting emissions that expires in 2012.

But Bush said on the sidelines of a Group of Eight summit that any global accord would have to include major developing countries that are quickly joining the ranks of top polluters.

"Our role is a bridge between people in Europe and others like India and China. If we want them at the table it is important that we give them the opportunity to set an international goal," he said.

"By 2008 the world's emitters of greenhouse gases should come together. Nothing is going to happen in terms of substantial reduction unless China and India participate."

German Chancellor Angela Merkel, the summit's host and a Bush ally, has piled on the pressure for Washington to agree binding targets on reducing greenhouse gas emissions and capping the rise of the planet's temperature.

Her aim is for the world's wealthy nations to take the lead in setting key benchmarks in the run-up to a United Nations meeting in Bali, Indonesia in December where a successor to Kyoto will be negotiated.

China, India and other developing countries, which have been invited to join the summit, are not required to make targeted emissions cuts under Kyoto -- a weakness Washington has frequently criticised.

The United States, the only G8 country that has not ratified the Kyoto Protocol, has flatly rejected any mandatory targets in a new pact.

Bush surprised many last week by offering a counter-proposal in which it and up to 14 other big emitters would agree by the end of next year "a long-term global goal" for reducing greenhouse gases.

Merkel has insisted that any agreement come within a UN framework, a condition Bush appeared to warm to at the summit.

Bush sharply rejected accusations that Washington was doing nothing to tackle climate change, telling reporters that US greenhouse gas emissions had declined in the last year despite the fact that the economy had grown.

"We are taking steps necessary to be good stewards of the environment and at the same time advance technologies," he said.

Blair said he saw progress at the summit in the German Baltic Sea resort of Heiligendamm on goals for slowing down the overheating of the Earth.

"I think there is a very substantial coming together around the need to make sure that we have a substantial reduction in emissions and find the right process and right way to achieve that," he said.

Blair has backed Merkel's goal of setting a binding cap on carbon emissions by 50 percent compared with 1990 levels by 2050 but acknowledged it was unlikely to be enshrined in the final communique of the G8 meeting with the five top developing nations.

"What we won't get and there was never any question of this, here and now amongst the G8 plus five, is the 50 percent (reduction in greenhouse gas emissions)," he said.

"What's important is that there should be such a target and that's the sort of ballpark we're talking about."

He said there was still hope that a clear benchmark on emissions would be set at the summit.

"It is possible that we leave this summit -- I am not saying that will happen -- with a commitment on the part of everyone to substantial reductions in greenhouse gas emissions by 2050 as a global target and that's of the order of the figures the Europeans are talking about."

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