Gordon Brown, the chancellor, today pledged to do what he could to help MG Rover clinch a joint venture agreement with China's biggest car maker.

Mr Brown, who is on a three-day visit to China, told BBC radio in Shanghai: "We have said to the companies and to the Chinese government we will do what we can in making this partnership successful."

MG Rover has been holding talks with Shanghai Automotive Industry Corp (SAIC) on a deal that would inject £1bn into the struggling British company and ensure the survival of MG Rover's Longbridge plant, near Birmingham.

British ministers have been lobbying Beijing hard over the negotiations as the absence of a deal could jeopardise some 6,000 jobs at Longbridge, less than three months before an anticipated general election.

"Both the Chinese and British governments will do what they can. In Britain's case, we are very supportive of this partnership," Mr Brown said. "The talks are designed to safeguard and maintain a large number of British jobs in the industry."

Under the deal, SAIC would take a 70% stake in a new venture to manufacture 1 million Rover-branded cars at Longbridge and in China. The closure of Longbridge could threaten as many as 45,000 jobs in the West Midlands area that depend on the plant.

MG Rover has been struggling to break even after being sold four years ago by Germany's BMW for just £10.

Mr Brown yesterday met the Chinese prime minister, Wen Jiabao, and the finance minister, Jin Renqing. The two sides said they planned to recommend reforms to the International Monetary Fund and World Bank to ensure they kept pace with increasing global trade and investment.

The chancellor also said Beijing should reform its foreign exchange system, but gradually - comments that contrast with those of US and some other European politicians who have urged China to move faster in loosening controls on currency dealings.

While in Shanghai, Mr Brown was due to visit the construction site of the 2010 World Expo and attend an event promoting educational cooperation between the two countries, before travelling on to the southern boom town of Shenzhen.

Britain is the single biggest European investor in China, pouring more than £10.4bn into the country each year. British and Chinese companies have set up more than 4,000 joint ventures, with trade growing by 230% over the past five years, Mr Brown's office said.