It is even described by US officials as a new focal point in Sino-US ties, which have often been marked by political and economic rifts.

China has responded with a cautious welcome, calling on the US and other developed countries to 'take the lead in cutting emissions, and providing funds and technical help'.

Despite positive, yet vague diplomatic rhetoric, mainland experts said neither side had offered much to end the impasse in the international climate talks and ignite change.

Renmin University professor Zou Ji said Mrs Clinton's visit was just the first step towards further communication, and the Beijing talks were unlikely to yield a substantial outcome.

'It will prepare the way for the G20 summit in London in early April, which will see the first meeting between President Hu Jintao and [US President Barack] Obama,' Professor Zou said.

He said recent academic reports in the US suggested closer co-operation between the world's two biggest polluters but failed to present concrete measures.

'Compared with the much more sophisticated economic co-operation such as the strategic economic dialogue mechanism between the two countries, climate co-operation has just begun,' he said.

Tsinghua University climate expert Liu Bin said the recent US remarks reflected the new American administration's diplomatic strategy of playing the climate card to put China at a disadvantage ahead of the Copenhagen talks.

'Mounting international pressure has already pushed the US to the brink of accepting its responsibility for climate change, which is long overdue. It wants to use China as a scapegoat,' Ms Liu said.

The US has been fiercely criticised for its refusal to ratify the 1997 Kyoto Protocol, which subjected industrialised countries to mandatory carbon emissions caps and was supposed to help developing countries adapt to rising temperatures.

Washington has long argued that the existing climate pact, which exempted large developing countries such as China, Brazil and India from emission reduction targets, was unfair and harmful to its economy.

Representatives from nearly 200 countries will meet in the Danish capital to agree on a successor climate treaty to Kyoto, which expires in 2012.

However, talks in recent years have reached a stalemate, with developed and developing countries wrangling over key issues such as carbon targets, technology transfer and funding for adaptation in poor countries.

Lin Erda, a veteran expert from the Chinese Academy of Agricultural Sciences said developed countries should take much of the blame for the 'we will only take on commitments if they do' stalemate.

Although developed countries are obliged to provide finance and technology to developing countries under the 1992 UN Framework Convention on Climate Change, a parent pact of Kyoto, little funding has been made available and hardly any technology has been transferred.

Experts agreed that funding shortages, which have plagued international co-operation for years and have been exacerbated by the unfolding financial crisis, would further delay bilateral collaboration.

'The previous US administrations, including those of George W. Bush and his predecessor Bill Clinton, offered little funding support for the international effort to address climate change. I don't see any possibility for a turnaround in US policy in the near future given the current economic situation in the US,' Ms Liu said.

The deadlock on technology transfer also proved difficult to break.

Ms Liu said developed countries and businesses were more concerned about losing their competitive edge than the disastrous effects of global warming.

'There has been much talk about the China threat. Why would industrialised countries be willing to offer China the latest climate-friendly technologies?' she said.

Ms Liu said the US and China were more likely to join hands in fields such as research on clean coal and renewable energy, and the development of electric cars.

Mainland experts said the extent of each country's commitment to tackling climate change should be decided by the level of economic development, and should not lower the living standards of ordinary citizens.

Although China was rumoured to have overtaken the US as the world's top carbon emitter, it was developed countries, including the US, that had contributed the most to global warming historically, Professor Lin said.

'The stalemate in fund-raising and technology transfer has already prompted questions about whether developed countries intended to contain China and other developing countries,' he said.

His views were supported by other mainland experts, who pointed out that per capita carbon emissions for China's 1.3 billion people were a fraction of that of rich countries.

Professor Zou said China did not have much room for compromise in Copenhagen. 'China will eventually accept the limits, but it is definitely not now or in 10 years. I think it will probably happen in 20 years when China's urbanisation is basically complete and most people lead decent lives in their houses with water and power supplies,' he said.

Jin Canrong, a Renmin University Sino-US affairs specialist, said Washington's new-found willingness to address climate issues was largely a result of pledges Mr Obama made during his election campaign.

Although both sides expressed intentions to improve co-operation, Professor Jin agreed that it was difficult to see how far the two countries were willing to go.

But he agreed that compared with a host of sensitive political, economic and financial issues, climate change was a good choice for both countries to foster closer ties.