Two workers look up at the huge arches and beams that will be part of the steel-and-glass dome covering the main stadium for the Athens Olympics. Representatives of the consortium building the roof, which has been designed by Santiago Calatrava, said that rehearsals for the opening ceremonies can begin in early July. But officials are anxious that they will have just three weeks in which to install the necessary equipment for the ceremonies and the broadcasting of the Olympics. Work to shift the massive arches supporting the roof over the stadium is expected to begin on April 18 and to last 15 days. Yesterday, former Culture Minister Evangelos Venizelos and other PASOK officials complained that the conservative government was over-dramatizing delays for political reasons as projects would be completed on time.