Top mainland leaders are concerned that the United States still has not committed itself to the 2010 World Expo, Shanghai organisers said yesterday. Wan Jifei, director of the event's executive committee, said the US had not given a formal, written commitment to take part in the expo, but had made a verbal promise. 'Our state leaders have conveyed concerns about the participation of the US. The Chinese ambassador in the US has also expressed the concerns,' Mr Wan said in Beijing. The absence of the US would deal a huge blow to the expo - billed as the biggest international event in the nation since the Olympic Games last year. Beijing is keen to use to event to promote the country's growing clout on the world stage. The Los Angeles Times reported in January that the US might not take part in the expo because organisers were struggling to raise funds for a national pavilion, with sponsorship drying up amid the global economic crisis. Shanghai World Expo Co-ordination Bureau deputy director Zhou Hanmin said the US pavilion preparation team's announcement last week that 3M Corp had become a sponsor was a positive development. None of the 231 countries and organisations that had pledged to attend the expo had pulled out, despite the financial crisis, Mr Zhou said. He said the expo would 'at least be able to make ends meet' and hoped 62 million tickets costing 160 yuan (HK$181) would be sold. 'We expect expo visitors to make 70 million trips, which is a conservative estimate. About 5-10 per cent will be overseas visitors including [those from] Hong Kong and Macau. Most of the rest will come from the Yangtze River Delta,' he said. The event has a budget of 18 billion yuan for venue construction and 10.6 billion yuan for operating capital. Funding would come from the central government, the Shanghai government and corporate sponsors, Mr Zhou said. The mainland won the right to host the World Expo in 2002, a year after Beijing succeeded with its bid to host the 2008 Olympics. Authorities hoped the two international events would showcase the nation's rising influence. It is still not known whether the Olympics were profitable or not. The Olympic organising committee had promised to make ends meet, or to make a slim profit. The nation's top auditor has admitted that his office had not yet looked into the spending for the Games. Information on the Olympics budget has been controlled tightly. While Beijing says the organising committee's operating costs and spending on venues totalled more than US$4 billion, overseas media has estimated a cost of US$43 billion.