The first piece of the sliding roof at Wembley Stadium has been lifted into place, but fresh concerns are emerging over whether the £800m stadium will be completed on schedule.

Brian Barwick, the chief executive of the Football Association, said yesterday that he did not have complete confidence that the 2006 FA Cup final would be held at the new venue as planned. "I do not know where the Cup Final will be held. I hope it is at Wembley," he admitted.

The Millennium Stadium in Cardiff has been booked as a precaution, in case the Australian construction company Multiplex is unable to deliver the stadium in time for two test events to take place before the FA Cup final in May.

Multiplex announced earlier this year that it had underestimated the cost of the project, prompting the resignation of its executive chair.