Cheered by euphoric workers and toasted with Greek wine, the Olympic Stadium's roof has begun its long-awaited slide into position in what is being hailed as a major turning point for the image of the August Games.

Watched on Monday by top International Olympic Committee officials on their final inspection of the city, the first of two arches that will hold an 18,000 tonne steel and carbon panel roof above the stadium in an Athens suburb began its centimetre by centimetre journey into position.

Over the coming days, the second arch will also be moved into position at the opposite end of the stadium so the latticed blue translucent roof, some of it already attached to the arches, can cover the 55,000 seat arena.

"Today we won the first bet," said deputy culture minister Fani Palli-Petralia, Prime Minister Costas Karamanlis's personal appointee in charge of catching up on badly delayed preparations.

Palli-Petralia broke a bottle of Greek white wine over the bottom of the arch seconds before machinery was set in motion to move the 70 metre high structure.

"UNIQUE GAMES"

Wine was also passed around dozens of workers who cheered and slapped each other on the back as the arch, about as tall as the Sydney Harbour Bridge, started its journey into position.

"Now we have the big bet to host a unique and safe Games," Palli-Petralia told more than 50 journalists present at the dusty construction site for the most anticipated -- and feared -- project after years of building.

"Today we responded to those who doubted that Greece can host unique Games. We are going to prove to them that Greece can do it."

The dome, designed by acclaimed Spanish architect Santiago Calatrava, will spread across the stadium like a giant spider's web lighting up the night in what many architects regard as an engineering challenge which bordered on the impossible because of the weights involved.

The roof slide started 10 days before a May 20 deadline set by the IOC which had warned if it was not underway by then the project would be cancelled and the Games would go ahead without a roof over the stadium.

"The start (of the first arch) went really well. We've done 10 centimetres without trouble and estimate it will be fully in position in about 12 hours," said Nikos Louridas, a spokesman for the main contractor involved in the project.

As well as protecting the stadium from rain, the roof's carbon panels will provide protection against soaring summer heat during the August 13-29 Games and has crucial broadcasting and surveillance cameras attached to it.

The successful start to the erection of the roof was much-needed good news for Athens Games organisers who, at the start of the 100 day countdown last Wednesday, once again found themselves under fire when three bombs went off outside an Athens police station.

More than half of the venues, as well as major infrastructure projects including new train and tram lines, are still many weeks from completion unlike for previous Games when most preparations were in place months before the opening ceremony.

Builders are working round the clock to meet deadlines and the IOC has said that thanks to the new frantic pace they expect all arrangements to be in place.

However the delays in major construction projects in the early years of preparations, mainly caused by political infighting, have meant some projects have been trimmed and landscaping work curtailed.