States are due to hold a global summit -- billed as the last chance to halt global warming -- in Copenhagen in December in order to agree on ambitious new targets for cutting the production of greenhouse gases.

Emerging economies, led by a skeptical India, have insisted that they can not sign up to such a deal unless the rich-world nations whose industry caused the problem pay billions to finance their transfer to new clean technologies.

Campaigners had hoped that under the chairmanship of US President Barack Obama the Group of 20 summit might agree to set aside 150 billion dollars to pay for this work and convince emerging economies to sign the deal.

The final summit statement ageed by the leaders, however, was fairly vague.

"We will spare no effort to reach agreement in Copenhagen through the United Nations Framework Convention on Climate Change negotiations," it said, without going into specifics of how the funding gap might be met.

Hopes that the world's leading powers would GET behind measures to help poorer countries fight climate change were raised in July in L'Aquila, Italy, when G8 leaders sent their finance ministers to seek sources of cash.

On Friday, however, the broader G20 group promised simply to "intensify our efforts" and sent the ministers back to do some more research.

"We welcome the work of the finance ministers and direct them to report back at their next meeting with a range of possible options for climate change financing," the final statement said.

Pressure groups were outraged, singling out Obama and Germany's Chancellor Angela Merkel for particular scorn.

"This is a crisis of leadership. The rich-country G20 leaders -- especially Merkel and Obama -- set themselves a deadline for a climate finance proposal, and then slept right through it," said Ben Wikler of Avaaz.

"Until the US, EU and Japanese leaders wake up and put together a serious climate finance plan, there will be a 150 billion dollar pothole on the road to Copenhagen," he told reporters in Pittsburgh for the summit.

Max Lawson, senior policy adviser for the aid agency Oxfam, said: "With 72 days to Copenhagen rich countries have once again refused to put up the funds needed to deliver the deal in Copenhagen."

The G20 did endorse an Obama-inspired plan to reduce government subsidies on fossil fuels, a move welcomed but dismissed as not enough by campaigners, but no-one was pretending the leaders made progress towards a Copenhagen deal.

Indian Prime Minister Manmohan Singh said the summit only took up global warming in broad terms and that he simply didn't know whether there would be a new deal to be signed in Denmark to replace the Kyoto protocol.

"I'm not an astrologer," Singh told a news conference dismissively.

"There is a broad, vague agreement that any agreement in which developing countries are also required to take any national action will have to be accompanied by credible action on the part of developed countries," he said.

"But other than expressing a pious wish with regard to the success of the framework convention meeting in Copenhagen, the Group of 20 I think did not go into the mechanics of these things," he said.

The Kyoto Protocol required rich nations to cut greenhouse gas emissions but the requirements expire at the end of 2012, and experts say emerging powers such as India and China must take part if a new plan is to succeed.

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