American David Zabriskie narrowly beat his former boss Lance Armstrong [Images] to win one of the fastest individual time trials in Tour de France [Images] history on Saturday.

Zabriskie, who left Armstrong's team this season to join Danish outfit CSC, beat the Texan by just two seconds at an average speed of 54.680 kph in the opening stage.

But Armstrong, bidding for a seventh consecutive Tour success, humbled all his rivals for overall victory and especially German Jan Ullrich, who he overtook three km from the finish on the small Atlantic island of Noirmoutier.

"When I saw I was making it back on Jan, I told myself I was not doing too bad," said Armstrong, who had set off a minute after his main rival.

"It's not a victory for me to overtake Jan. He had a crash yesterday in training, but it made me realise I was in good form," Armstrong said at the finish.

Zabriskie's victory was not really a surprise as the 26-year-old from Salt Lake City is a specialist who won one of the main time trials in the last Giro d'Italia in Firenze.

"I didn't think I could beat Armstrong today," said Zabriskie, who is taking part in his first Tour.

The two Americans left the rest of the field far behind in one of the fastest such events on the Tour.

In 1994, Briton Chris Boardman won the Tour prologue at 55.152 kph, but over a much shorter distance of 7.2 km around Lille.

Sunday's Tour curtain raiser from the mainland of Vendee to the island of Noirmoutier was a 19 km individual time trial into a strong headwind, which should have hampered performances.

GOOD OPERATION

But Zabriskie beat the fastest average speed for a time trial over a comparable length set by compatriot and three-time Tour winner Greg LeMond in 1989. LeMond rode the 24.5 km of the Tour's final stage between Versailles and Paris at 54.545 kph.

The ride between Fromentine and Noirmoutier, a small island off the Atlantic coast, was for specialists only -- a long straight and flat stretch favouring power and velocity.

The strong headwind and cloudy weather made it an even harder Tour opener, but Armstrong amply dismissed all doubts that he might lack motivation and preparation this year.

Although he failed to take the yellow jersey on the first day, Armstrong has seen his leading rivals lose precious time right from the start.

Kazakhstan's Alexander Vinokourov, who was third, has already lost 51 seconds to Armstrong. Floyd Landis, another of Armstrong's former team mates, is just a minute behind him while Ullrich sits 1:06 behind the Tour champion.

"It's unbelievable what Lance did today. It's undoubtedly a good operation," his team director Johan Bruyneel said.

The first stage of Armstrong's final Tour started badly for the Discovery Channel leader as his right foot skidded off the pedals after 100 metres, but the incident only spurred him into action. The six-time champion will retire after the Tour.