Dubai: The world's tallest tower, the $900 million Burj Dubai, is months off schedule after its cladding work timetable was thrown into disarray last year, officials admitted.

Current work on what will become the world's tallest building is "a couple of months" behind schedule, due mainly to the bankruptcy of Swiss-based curtain walling giant Schmidlin last year, the parent company of Schmidlin LLC, which was contracted to install exterior cladding on the still-exposed concrete tower.

"We had a problem with one of our partners on our curtain wall cladding and this had an impact on the site," said Greg Sang, Emaar's assistant director of projects and the man overseeing the entire $20 billion Downtown Burj Dubai development.

"We've got a new contractor on board and they are working very hard to catch up. At the rate they are making progress they should be able to do this."

Sang denied that construction would be complete up to a year later than its scheduled fourth quarter 2008 delivery date.

"We've got probably a couple of months in delay, but the final completion date is unchanged. We're still on schedule for the end of 2008," he said.

The Burj Dubai's exterior cladding not only has to protect the tower from Dubai's scorching temperatures and high dust levels, but also has to withstand strong winds, said Sang.

"Wind management is probably the most critical engineering challenge that we face. We have to minimise the movement so it's not uncomfortable. At most it will move 1.5 metres at the top," he said.

The final floor count of Dubai's mega project is still unknown, with project developers Emaar Properties refusing to comment on rumours that design changes have altered the final height of the building.

"We decided the final floor count but it's still confidential.

"We're currently at 103 floors and all we're saying is that it will be more than 160 floors when finished," said Sang.