Expo tickets for the month of October are in high demand, with two dates in particular - Oct 1 (China's National Day and China Pavilion Day) and Oct 31 (the date of the closing ceremony) - being the most popular.

"I've tried four of the appointed agencies - China Mobile, China Telecom, Bank of Communications and China Post - but failed to get a single ticket for the closing ceremony," said Yu Wei, of Jiaxing in Zhejing province.

His next attempt was to post a thread on an online forum, asking for an Oct 31 Expo ticket, but he has yet to receive a reply.

According to the official website of Expo 2010 Shanghai, "organizers are to stop selling standard-day and multi-day tickets to control the number of visitors during the event's final two months".

The Expo ticketing center said that only tickets bought at the gate, and tickets sold for 14 specific days (Oct 1 to 7 and Oct 25 to 31), will be available from Sept 1.

China Mobile, China Telecom, Bank of Communications and China Post are the only four agencies entitled to sell tickets for the 14 appointed days, which are priced at 200 yuan each.

"Based on the current statistics, 18 million visitors have purchased Expo tickets but haven't come yet, which puts more pressure on Expo traffic before it closes," said a spokesperson for the China Youth Travel Service in Anhui province, who declined to be named.