More than 50 incumbent heads of state or government have expressed intention of visiting Shanghai to see the World Expo that is scheduled for May 1 to October 31, organizers told Xinhua Thursday, which witnessed the 100-day countdown for the six-month-long mega event.

Five trial operation activities will be held at the end of April to check up exhibition pavilions, security and volunteer arrangements, visitor services and logistics for the Expo, sources with the Bureau of Shanghai World Expo Coordination said.

The whole city would be motivated for the last trial, and 500,000 people will take part in the drill, the sources added.

Expo as economic propeller

To date, 192 countries and 50 international organizations have confirmed their participation in the global feast that usually showcases latest advances of architecture and engineering worldwide.

Despite the global economic downturn, no would-be participants have decided to withdraw from the Expo.

Leo Delcroix, commissioner general of Belgian section at the Expo, said that at a time when the western developed economies remained in recession, a savvy policymaker should grasp the opportunity to be offered by the Expo to make preparations for a new-round growth.

Delcroix said that the world economy needed to take a year and a half to recover, during which the Expo would be held. It would be a good chance to showcase to the rest of the world, he added.

Many future participants used to face with such challenges as crisis effect, currency depreciation and budget slash during their preparation for the Expo. But they hold on. The construction of the US pavilion, which had met difficulties in fundraising, is an example.

The United States signed participation contract as late as last July. Construction of the US pavilion began on July 17, and the topping-off finished in October. On November 16, US Secretary of State Hillary Clinton paid a visit to the Expo site and appealed for sponsorship for the pavilion, since US laws prohibit the government from allocating money directly for the Expo activity.

According to Nicholas Winslow, president of the US pavilion, 85 percent of the US$61 million participation cost has been raised, and the construction work will be completed in early March.

"The pavilion will not be a trade show. It will be an opportunity for America to showcase itself to the world," Winslow said.

The Saudi Arabian pavilion, which costs more than 1 billion yuan (US$146.6 million), will be completed in mid February. Designed jointly by Saudi Arabian and Chinese architects, the pavilion symbolizes "the marine Silk Road" from China to the Western world, and will witness the largest human and financial resources the Arabic nation will ever put into the Expo activity.

Russia used to participate in world expo by renting an exhibition venue. But this time, it spent more than 1.5 billion rubles (US$52.8 million) to build its own pavilion.