Lance Armstrong [Images] seized the Tour de France [Images] yellow jersey in dramatic fashion on Tuesday when his Discovery Channel team sped to victory in the fourth stage ahead of the CSC outfit of previous leader David Zabriskie, who crashed near the finish.

Armstrong's team set too fast a pace over the 67.5 km team time trial between Tours and Blois, clocking one hour, 10 minutes and 39 seconds at an astounding average speed of 57.31 kph, the fastest in a Tour.

Zabriskie, winner of Saturday's opening individual tiThe American's Discovery Channel team clocked one hour, 10 minutes and 39 seconds at an average speed of 57.31 kph, the fastest in a Tour.me trial, crashed in the final two kilometres of the stage when his chain snapped and lost 1:28 on Armstrong.

His CSC team mates were just two seconds slower than Armstrong's outfit on the line, meaning the 26-year-old American would probably have retained top spot had he not crashed.

Instead it was business as usual for six-times champion Armstrong. He holds a 55 seconds lead over team mate George Hincapie.

JERSEY BONUS

"It was more or less the plan. We first of all wanted to win the stage but to get the jersey on top is a bonus," said Armstrong.

"It feels very good actually, for a few reasons -- it's always good to win this event and show that the team is strong. It's also the first yellow jersey for Discovery Channel, a company that came in and supported us for a long term, a three-year commitment.

"It's nice to give them their first", said the 33-year-old.

Discovery Channel replaced US Postal as the Texan's team sponsor this season.

After only four days, Armstrong, riding the Tour for the last time, has a commanding lead. The first rider from another team in the overall standings is third-placed German Jens Voigt, of CSC, who lies 1:04 behind.

Germany's [Images] Jan Ullrich's, whose T-Mobile outfit was third in the stage, is 14th, 1:36 adrift of Armstrong while Kazakh team mate Alexander Vinokourov is 1:21 behind.

CSC's leader Ivan Basso trails Armstrong by 1:26 in the same time as Zabriskie.

Armstrong is ideally placed in his quest for an unprecedented seventh Tour win and everything is, as usual, going to plan.

CRASH UNEXPECTED

Zabriskie's crash was unexpected but it might also have had something to do with the frantic pace set in the struggle between the Discovery Channel and CSC teams.

"It's unfortunate. I wish I could comment more, but I could not really see what happened," Armstrong said.

"The team time trial is so hard at the end that everybody is at the limit. When we came into the city, there were lot of turns, and it's easy to make a mistake like that.

"Bad luck for him but he is a young an gifted rider and I'm sure he'll be in the yellow jersey again in the future."

Regardless of Zabriskie's misfortune, Armstrong's performance was impressive as he played a leading part in his team's effort.

Discovery Channel's teamwork and a strong tailwind helped them ride the fastest tour stage ever.

The previous highest average speed had been set by Briton Chris Boardman in the 7.2-km prologue in 1994. The fastest team time trial was ridden at an average of 54.93 kph by Italian crew Gewiss Ballan in 1995.

Wednesday's flat 183-km stage to Montargis should suit the sprinters and Armstrong's team director Johan Bruyneel made it clear his team would not defend the yellow jersey if it required too much effort.

"Our goal is to win in Paris and if that means, in certain race conditions, another guy or team takes the jersey, then that's the way it's going to be."