Athens organisers have postponed the installation of a huge steel dome above the main Olympic stadium just 101 days before the opening ceremony.
Two giant arches are waiting to be moved into place over the main Olympic stadium
The roof was due to put in place at the weekend but contractors need more time to prepare for the final assembly.
The International Olympic Committee has said that if the two arches are not in place by 20 May, the project would have to be scrapped.
The operation is expected to start on Friday in a rush to beat the deadline.
The roof is the biggest concern for organisers who have repeatedly shifted the date to slide the huge arches, which will carry the 18,000-tonne steel roof.
The IOC has expressed concern over the roof, which is not a key Olympic project, for the past two years.
Last week contractors in Athens blamed details involved in organising the sliding of the arches and the fear of windy weather for the hold-up.