The exterior of the United Nations headquarters in New York where climate talks will take place ahead of the summit in Copenhagen. Photograph: Michael Crabtree

China and India appeared poised for bold new action on climate changeahead of a major UN summit tomorrow, in moves that will significantly increase pressure on President Barack Obama to deliver cuts in US emissions.

The UN climate chief, Yvo de Boer, said today that he expects China's president, Hu Jintao, to announce a series of new measures tomorrow that would put the country well ahead of America in dealing with climate change. Meanwhile, India's environment minister, Jairam Ramesh, told the Guardian his government planned to make "aggressive" cuts in India's emissions.

The Chinese and Indian measures — if fully realised — could represent a breakthrough in bringing them into a global climate change deal at a UN summit in Copenhagen in December. Almost all observers say the Copenhagen talks are danderously stalled..

"This suite of policies will take China to be a world leader on addressing climate change, and it will be quite ironic to hear that expressed tomorrow in a country (the United States) that is firmly convinced that China is doing nothing to address climate change," De Boer said.

China, India and other developing countries between them will account for more than two-thirds of the world's emissions by 2020, but they argue they cannot sacrifice economic growth and poverty relief to reducingcarbon emissions, especially if the industrialised world does not take decisive action on its own emissions.

But China and India now appear to be demonstrating a new willingness to act — even in the absence of a firm commitment from America, where Obama is struggling to deliver on a promise of an economy-wide plan to cut greenhouse gas emissions.

In an interview with the Guardian, India's environment minister, Jairam Ramesh, sketched out a series of measures he said would go some distance to cutting India's emissions, so-called mitigation measures. "India is going to aggressively take on voluntary mitigration outcomes," he said. "We are now going to go for domestic legislation [which] will enshrine some targets."

These include a mandatory fuel efficiency target which would come into effect in 2011; a more energy efficient building code which would come into effect in 2012; and an increase in electricity produced from renewable sources to 20% by 2020. The government was also stepping up efforts to stop deforestation, raising its target for tree cover to 15% by 2020. He said these measures and others were designed to reduce India's energy intensity by a further 5 to 10%.

"What India is going to do is to set a target date which is 2020 and introduce a quantitative outcome which is an implicit mitigation target — not explicit target. We will enshrine that into law so that there is a degree of credibility."

However, Ramesh said India would not compromise on its ambitions of achieving 8% economic growth a year. The plans could also fall hostage to India's political scene, where there are sensitivities at being seen to be giving in to pressure from the developed world.

Ed Miliband, the climate change secretary, said that recent moves by India, China and other developing nations had improved the chances of a comprehensive global warming deal at Copenhagen. But, writing in tomorrow's Guardian, he warned that a new kind of diplomacy was needed: "We must be in this together rather than looking for who to blame. The fate of every nation on earth hangs on the outcome of Copenhagen. It is too important to play the cards close-to-your-chest poker games that marked diplomacy of the 20th century."

Miliband also noted a new report from economist Lord Stern which showed that, even with the limited commitments so far, the world was within striking range of meeting 2020 targets for cutting emissions sufficiently to keep the earth from warming beyond 2C. Stern, in a speech at Columbia University later today , was expected to present a report showing the world was on course to reduce overall emissions from today's global total of 50 gigatonnes to 48 gigatonnes. That is not so far off the figure of 44 gigatonnes needed to avoid catastrophic global warming. Emissions, in the absence of the actions so far agreed, would rise to 65 gigatonnes by 2020.

However, leaders of countries on the sharp end of climate change did not share Miliband's optimism. Bharrat Jagdeo, Guyana's president, told The Guardian he feared the deal now beginning to take shape could seriously weaken targets for reducing emissions compared to the targets demanded by scientists. That would be a calamity for Guyana, which loses some 10% of its GDP annually to flooding.

Jagdeo said he was worried about what sort of funds would be established to help shield poor countries from the worst effects of climate change.

"The negotiation process is not leading to the type of agreement that we want in Copenhagen," Jagdeo said. "We have basically farmed out the negotiations to technical people and most of them are at the limit of what we can agree to. What we need are leaders to break their silence and come up with new policies. "

Ramesh also had reduced expectations for Copenhagen. He held out little hope of a broad agreement to cut emissions that will keep global warming within 2C, a view echoed in an influential report in China last week. Instead, in his view, there was only broad agreement on the need for a fund to protect poor countries from the worst ravages of climate change, a plan to help developing countries adopt new clean energy technology, and another programme — with funding from the industrialised world — to reduce deforestation in the developing world. " It's an easier option if you don't have to change your lifestyle, you don't have to cut emissions directly. All you have to do is put some money into a forest in India or Papua New Guinea or somewhere," Ramesh said.

The UN is hoping to break through that pessimism by getting world leaders directly involved with climate change at the summit on Tuesday and beyond. The prime minister, Gordon Brown, has agreed to go to Copenhagen and is encouraging other leaders to attend the negotiations in the hopes of producing a stronger agreement. "This is too important to be left to the negotiators. Negotiators have their role but leaders are the people who are going to make this happen," said Miliband.

THE UNITED Nations climate change conference in Copenhagen in December is sometimes described as a last chance to avert catastrophe on a global scale; and that is on the less extreme end of the debate.

While it can be unhelpful to cast green issues always in terms of impending apocalypse, it is important to state how much rides on the success of the summit, especially since, as the Observer reports today, the prospects of a deal are receding.

The Copenhagen conference is supposed to negotiate a replacement to the 1997 Kyoto Protocol, the landmark deal that first bound nations to cut greenhouse gas emissions. Its provisions start expiring in 2012.

There is scientific consensus that Kyoto's successor should cut carbon emissions to the point that average temperatures do not rise by more than two degrees Celsius. Any more than that would risk ecological changes of devastating proportions. In practical terms, that means binding targets so that the rate of emissions stops growing immediately and starts falling by 2015. By 2050, say UN scientists, they should be cut by 80%.

There are various obstacles in the negotiations, but the main one is a global fault line between developed and developing worlds. Countries with massive industrial potential still unfulfilled – mainly China and India – will not take moral instruction in eco-austerity from countries that have already industrialised and left a legacy of carbon in the atmosphere as a result.

The industrialised countries, meanwhile, are reluctant to bind themselves to targets that do not also restrain countries they see as competitors.

The theoretical framework for a compromise is broadly in place: the developed world must accept its responsibility for old pollution and make amends by subsidising low-carbon energy in the developing world. In exchange for redistribution of green technology from rich to poor, the developing world would accept significant emissions targets.

Turning that framework into a treaty will be hard. But global leaders have shown in their response to the financial crisis that fear of catastrophe can galvanise co-ordinated and collective action. They ought to fear climate catastrophe and they are running out of time to act.