A total of 158 countries, regions and international organizations have confirmed their participation in the 2010 World Expo to be held in Shanghai.

Yang Xiong, Vice mayor of Shanghai and member of the organizing committee for the World Expo 2010 Shanghai China, made the announcement at a news conference in Beijing on Tuesday.

The organizing committee forecast that more than 200 countries, regions and international organizations are expected to attend the 184-day event.

"The international community is reacting positively to the event and we receive a confirmation letter every three days," Yang said.

Research shows that a total of 70 million people will visit Shanghai during the event and the daily number may reach 800,000, Yang said, adding that transportation will be the biggest challenge.

"The subway will be the solution," Yang said, "Shanghai will have 230 kilometers of subway in operation by 2007 and it will have 400 kilometers by 2010."

Shanghai will also take other measures to fight traffic congestion, such as forbidding private cars from entering the expo park, Yang said.

Shanghai is also expanding its airports, railway stations and highways to accommodate such an enormous passenger flow, Yang said.

By 2010, 60 highways, connecting Shanghai and its neighbouring Jiangsu and Zhejiang provinces, will be finished, Yang said.

"By using new energies, such as solar power, there will be no emissions from the expo park," Yang added.

The 2010 World Expo in Shanghai will be held from May 1 to October 31.