Premier Wen Jiabao called on Washington to ease Beijing's worries about its huge holdings of US government debt and urged swift reform of the International Monetary Fund as he laid down markers for next month's Group of 20 summit. Mr Wen also pledged the central government would introduce more stimulus measures if economic hardship worsened. 'We have made a huge amount of loans to the United States. Of course we are concerned about the safety of our assets. To be honest, I'm a little bit worried,' Mr Wen said at the closing press conference of the annual national legislative session. 'I would like once again to request that the United States maintain its creditworthiness, keep its promise and guarantee the safety of Chinese assets.' He said China had already decided to diversify its foreign exchange reserve holdings. Last month, on a trip to Beijing, US Secretary of State Hillary Rodham Clinton encouraged China to keep investing in US assets and said any big switch out of Treasury bonds would drive prices lower, inflicting the very losses Mr Wen fears. Nearly half China's US$2 trillion (HK$2.25 trillion) in currency reserves is invested in US Treasury bills and other US government debt. Mr Wen hinted that Beijing was willing to increase its contributions to the IMF if it was reformed to better reflect the developing world's interests. The US and other developed nations are pressing Beijing to pay more into the fund. Tang Min, deputy secretary general of the State Council's China Development Research Foundation, said: 'The IMF must be restructured to supervise financial markets in the developed world, not just developing markets.' On Wednesday, US Treasury Secretary Timothy Geithner urged Group of 20 nations to take forceful action to end the global financial crisis and the IMF to expand its supplementary borrowing programme by about US$500 billion. President Hu Jintao will attend the G20 meeting in London on April 2, on the sidelines of which he is expected to meet his US counterpart, Barack Obama. The world is watching to see what role China will play at the summit. On the economy, Mr Wen said 'confidence is more important than gold'. 'We have prepared contingency plans to handle greater difficulties,' he said. 'We have enough ammunition and we can launch new economic stimulus policies at any time.' Mr Wen disappointed investors a week ago in his annual report to parliament by failing to unveil an increase in the 4 trillion yuan stimulus package announced in November to boost domestic demand and counter a plunge in mainland exports. Despite Mr Wen's comments, mainland stock markets fell for a third day in a row. Mr Wen warned achieving Beijing's 8 per cent target for economic growth this year would be tough. The government has attached great importance to attaining rapid growth, and sees an 8 per cent expansion as crucial to maintaining social stability. Millions of migrant workers have already lost their jobs.