A high-powered group of senior Republicans and Democrats led two missions to China in the final months of the Bush administration for secret backchannel negotiations aimed at securing a deal on joint US-Chinese action on climate change, the Guardian has learned.

The initiative, involving John Holdren, now the White House science adviser, and others who went on to positions in Barack Obama's administration, produced a draft agreement in March, barely two months after the Democrat assumed the presidency.

The memorandum of understanding was not signed, but those involved in opening up the channel of communications believe it could provide the foundation for a US-Chinese accord to battle climate change, which could be reached as early as this autumn.

"My sense is that we are now working towards something in the fall," said Bill Chandler, director of the energy and climate programme at the Carnegie Endowment for International Peace, and the driving force behind the talks. "It will be serious. It will be substantive, and it will happen."

The secret missions suggest that advisers to Obama came to power firmly focused on getting a US-China understanding in the run-up to the crucial UN meeting in Copenhagen this December, which is aimed at sealing a global deal to slash greenhouse gas emissions. In her first policy address the secretary of state, Hillary Clinton, said she wanted to recast the broad US-China relationship around the central issue of climate change. She also stopped in Beijing on her first foreign tour.

The dialogue also challenges the conventional wisdom that George Bush's decision to pull America out of the Kyoto climate change treaty had led to paralysis in the administration on global warming, and that China was unwilling to contemplate emissions cuts at a time of rapid economic growth.

"There are these two countries that the world blames for doing nothing, and they have a better story to tell," said Terry Tamminen, who took part in the talks and is an environmental adviser to the governor of California, Arnold Schwarzenegger. The nations are the top two polluters on Earth.

The first communications, in the autumn of 2007, were initiated by the Chinese. Xie Zhenhua, the vice-chairman of the National Development and Reform Commission, the country's central economic planning body, made the first move by expressing interest in a co-operative effort on carbon capture and storage and other technologies with the US.

The first face-to-face meeting, held over two days at a luxury hotel at the Great Wall of China in July 2008, got off to a tentative start with Xie falling back on China's stated policy positions. "It was sort of like pushing a tape recorder," said Chandler, "[but after a short while] he just cut it off and said we need to get beyond this."

The two sides began discussing ways to break through the impasse, including the possibility that China would agree to voluntary – but verifiable – reductions of greenhouse gas emissions. China has rejected the possibility of cuts as it sees that as a risk to its continued economic growth, deemed essential to lift millions out of poverty and advance national status.

Taiya Smith, an adviser on China to Bush's treasury secretary, Hank Paulson, who was at the first of the two sessions, said: "The thing that came out of it that was priceless was the recognition on both sides that what China was doing to [reduce] the effects of climate change were not very well known," she said. "After these discussions was a real public campaign by the Chinese government to try to make people aware of what they were doing. We started to see the Chinese take a different tone which was that 'we are active and engaged in trying to solve the problem'."

During the second trip to China by the Americans, Xie suggested a memorandum of understanding between the two countries on joint action on climate change.

Chandler said he and Holdren drew up a three-point memo which envisaged:

•Using existing technologies to produce a 20% cut in carbon emissions by 2010.

• Co-operating on new technology including carbon capture and storage and fuel efficiency for cars.

• The US and China signing up to a global climate change deal in Copenhagen.

"We sent it to Xie and he said he agreed," said Chandler.

The ties were further cemented when Gao Guangsheng, the leading climate official, attended Schwarzenegger's global meeting on climate in November last year. Obama, who had been elected president two weeks earlier, addressed the gathering by video.

By the time Xie visited the US in March, the state department's new climate change envoy, Todd Stern, and his deputy, Jonathan Pershing, were also involved in the dialogue. But the trip by Xie did not produce the hoped-for agreement. Both Stern and Holdren declined to comment when asked by the Guardian.

Those involved agree it was premature to expect the Obama administration to enter into a formal agreement so soon in its tenure. Additional members of the US team included Terry Tamminen; Jim Green, adviser to Joe Biden, now the vice-president who then headed the Senate foreign relations committee; Mark Helmke, adviser to Richard Lugar, the ranking Republican on the committee; and Frank Loy, a former state department negotiator on climate. Both Green and Loy have been nominated to jobs in the Obama administration.

Chandler and Smith believe the effort will pay off in a more comprehensive deal between the two governments. "Xie came to visit the US when the administration was still trying to figure out its standing on climate issues and it was without very much staff," said Smith. "I don't see this as a dead issue at all. I think it's something you would consider still in process."