Greek officials declared victory on Monday in the race to complete the reconstruction of the original Athens Olympic marathon route less than three weeks before the start of the Games.

After years of delays and recent financial obstacles, organisers delivered 26 revamped kilometres of the 42.195 kms route near the monument of the 490 B.C. victory of the Athenian army against the invading Persians four days before an International Olympic (IOC) deadline expired.

The remaining 16 kms weave through Athens along an already widened boulevard.

"We have won," a smiling Public Works Minister George Souflias said, using the famous phrase of the Athens messenger who ran the first marathon to announce victory over the Persian army before dropping dead of exhaustion and dehydration.

"We are winners because the marathon route is the symbol of the Olympic Games in Athens. With delivery of this project we have won the first big bet."

Major renovation work on part of the route, one of the highlights of the Athens Games, started early last year, after years of squabbling, delays and changes in the designs.

Originally due for completion last year, the widened route, tracing the footsteps of messenger Phidippides who ran back to the capital to declare victory against the Persians, is one of the most anticipated events of the Games.

The IOC had warned earlier in the year that the road had to be ready by the end of July to allow for testing and other landscaping-type work ahead of the Games opening on August 13.

Organisers had to scrap ambitious plans for the construction of a large monument at the start of the race due to time constraints.

Runners will start near the site of the ancient battle and finish at central Athens' Panathenian stadium, the same route as the first modern Games in 1896.

The project was thrown into disarray earlier this year when the original road contractor went into bankruptcy partly because of overtime payments and poor construction.

As recently as May, builders were ripping out and repairing parts of the badly reconstructed route after the contractor's business folded.