Fabian Cancellara got the better of Alberto Contador to triumph in the 15.5km time-trial first stage in Monaco.

The 28-year-old Saxo Bank rider, the reigning Olympic time-trial champion, powered home in a time of 19 minutes 32 seconds to claim the yellow jersey.

Cancellara finished 18 seconds clear of Spaniard Contador, who edged Great Britain's Bradley Wiggins (Garmin-Slipstream) by a second.

Contador, the 2007 champion, was one of four Astana cyclists in the top 10 with German Andreas Kloden fourth, American Levi Leipheimer sixth and seven-time champion Lance Armstrong 10th.

American Armstrong, who came out of retirement in January after quitting following the 2005 Tour, was 40 seconds down on Cancellara.

Carlos Sastre (Cervelo), the defending champion from Spain, was a further 26 seconds back in 21st spot.

The Tour continues tomorrow with the 187-kilometre second stage from Monaco to Brignoles.

Contador, who claimed the first polka dot King of the Mountains jersey, insisted after the prologue that there was no unrest within the highly competitive Astana team.

"I really couldn't care less," he said of such speculation. "The media are hyping this up and talking about a conflict but the atmosphere within the team is and will stay good.

"We must work together to win this Tour de France.

"I'm in good form. Now I hope to stay at that level.

"With Levi, with Lance, we're all going to work hard for Astana to win the Tour."