Mock-up of the proposed tower in Shanghai

But a spokesman for the Japanese consortium behind the Shanghai project, the Mori Building Company, said plans were being reviewed to make the building "better, stronger and safer".

The planned Shanghai World Financial Centre in the eastern city of Shanghai, is to reach 460 metres (1,509 feet).

It is hoped the building will open before Beijing hosts the 2008 Olympics.

Mori Building Company, said the 11 September attacks, in which two hijacked passenger jets were flown into the 110-storey World Trade Center, had not altered the plans.

"The terrorist attacks were extremely regrettable. But the case was totally an exception, which no one was able to expect," said company spokesman Kiyoshi Yoshikawa.

"Mori Building plans to continue going ahead with the project as scheduled."

Safety features

If completed as planned in 2007, the 94-storey Shanghai tower would take the title of world's tallest building from Malaysia's Petronas twin towers, at 452 meters (1,492 feet). The building is forecast to cost $625m.

World's tallest buildings

Petronas twin towers, Kuala Lumpur: 452m Sears Tower, Chicago: 442m Jinmao Tower, Shanghai 421m

The glassy building, with a round hole near its top to relieve wind pressure, is to be built just blocks from the 88-storey Jinmao Tower, currently China's tallest building and the third tallest in the world.

However, under a review process that has been going on since October 1998, the firm said it would look into measures to improve the security of the building.

"It is very clear we will strengthen the structure of the building. We will improve the security of the building," said Kiyoshi Yoshikawa.

The existing plans for the new building include a dedicated fire lift and refuge floors at every 15 levels.

Refuge floors contain no furniture and are designed to be totally fire proof so that they can harbour people in the middle of an evacuation.