Lance Armstrong moved into control of the Tour de France with a blistering burst of speed going up the final climb of stage 10.
He pulled out a minute on Ivan Basso and more sizeable gaps on the T-Mobile trio of Jan Ullrich, Alexandre Vinokourov and Andreas Kloden.
The stage victory went to Alejandro Valverde, who outsprinted Armstrong in a thrilling finale.
But Armstrong's second place was enough to move him into the yellow jersey.
1629: Armstrong now boasts a 38-second lead over Rasmussen in second in the overall standings. Ivan Basso is another two minutes back in third. Ullrich, though, has four minutes to make up if he is to win the Tour.
1626: It's been a miserable day for Vinokourov. He comes over the line with Bobby Julich 5m18s behind Armstrong. His look up at the clock says it all.
1622: Basso, virtually frothing at the mouth, comes over the line a minute back from Armstrong, with Ullrich more than two minutes back. Now will be the time for them to start counting their losses.
1621: Valverde springs past Armstrong in the final metres for a breathtaking win. Armstrong will hardly be too fazed, though, having put massive time gaps on some of his leading rivals for overall victory.
1620: And Armstrong goes for it with Valverde to the line and a final sprint.
1619: Rasmussen goes for it but the others stick with him. It's destined for a sprint finish...
1618: The nervous glances come into place from the front four now as they jockey for final position under the 1km-to-go barrier.
1617: Valverde has been tipped as the next Armstrong by many. It remains whether he has the ability to match him at the stage finish in what is his first Tour.
1615: The cat and mouse games for the stage win look set to begin shortly. Rasmussen will fancy his chances as will Valverde, always a strong finisher. But it remains to be seen how much Armstorng's got left in his legs. He nonchalantly zips up his jersey with just 2km left.
1612: Armstrong calls for the others with him to come through. But the pain on their faces is a total rejection of the Texan's invite. There's just 4km left.
1610: Mancebo, seemingly giving everything, moves ahead to protect his team-mate Valverde and give him all the help possible. Further back, though, Ullrich is already 1m20s behind the Spanish duo, Armstrong and Rasmussen. The overall standings look set to be well and truly shaken up.
1605: Armstrong's rivals must think it's relentless now. Basso is absolutely blown out of the back after the latest Armstrong attack. The American still has time to keep on chatting to his rivals. Further down Kloden is coaxing Ullrich up the ascent. There's 6.5km to go.
1602: And then there were five - Armstrong, Valverde, Mancebo, Rasmussen and Basso. Armstrong looks in awesome condition.
1600: Cadel Evans is the lastest man failing to keep up with Armstrong's pedal power. With 10km left, Armstrong moves into the race lead but looks to his other riders for support. Mancebo and Valverde do the honours.
1557: Jan Ullirch is left slogging his way up to Courchevel on his own and has pain etched all over his face. Basso, Valverde, Rasmussen and Mancebo are keeping up with Armstrong. And they now have Jaksche in their sights.
1555: There are just a handful of riders with Armstrong after Vinokourov is remarkably dropped. Popovych gets orders from Armstrong for one final drive and he gives it everything before his more experienced team-mate then moves to the front.
1552: Finally Hincapie peels off for his lonely ascent to the climb. But more crucially Vinokourov is at the back of the Armstrong group. He looks a little out of sorts... for now.
1550: Just Popovych and George Hincapie remain with Armstrong from his Discovery team. The Texan is sandwiched between Vinokourov and Valverde. It's only a matter of time surely before someone makes a move. There are 13km to go.
1546: Yet more riders drop off. Christophe Moreau, who had hoped to move into yellow after the stage, has tired suddenly. Meanwhile, Carlos Sastre darts in front of the Discovery riders.
1541: Shouts go up left, right and centre on the mountain. Among the latest big names to be left begging are Roberto Heras - many people's tip to win the stage, Joseba Beloki, Denis Menchov and Brad McGee.
1536: Ullrich and Vinokourov are literally breathing down the neck of Armstrong, who still has five Discovery riders with him. Further upfield, Jaksche breaks clear of Pereiro with 17km left.
1531: The pace is too much at the front for most of the breakaway riders as Jaksche and Pereiro show off their superior climbing ability. Further back, Voigt - the yellow jersey wearer - is dropped by the Armstrong group.
1529: A light-blue train of Discovery riders lead the main challengers up to Courchevel. Their blistering pace is already having a devastating effect, although the likes of Ullrich, Vinokourov and Basso remain in contention.
1518: It's very much the calm before the storm now. The riders are moments away from starting the climb up to Courchevel.
1509: At the head of the field, the leaders are reunited but Pereiro (19th overall at 5m12s) and Jaksche (23rd at 5m20s) will not be allowed to get away for long by the chasing Discovery boys.
1502: There's a frightening tempo being set by the Discovery train. They are certainly laying down the gauntlet to their rivals ahead of the climb up to Courchevel.
1450: Sanchez rejoins Brochard at the front.
1438: Brochard is now clocking some 90km/h going down the descent and has shaken off his other breakaway riders out front. Meanwhile, Armstrong's team-mate Yaroslav Popovych comes off his bike. He's back into the swing of things pretty soon.
1426: Brochard goes over the top of the Cormet de Roseland at the front of his five-man break. Armstrong and the main contenders come over it 3m45s behind them. Mayo seems to be the only real contender not in that pack.
1410: The likes of Valverde, Garzelli, Mancebo etc are brought back into the peloton as Armstrong's Discovery Channel team lift the tempo. Posthuma, Facci, Brochard, Krivstov, Sanchez still lead Armstrong et al by 4m30s.
1402: Iban Mayo comes off the back of the peloton on the climb and looks in trouble. Meanwhile his countryman Alejandro Valverde flies up the road. It's chaotic but thrilling stuff.
1353: There are less than 10km to go to the summit and Brochard has opted to up the pace. It's split the leading seven. Meanwhile, others pull off the front of the main group. The big names to go clear and try to peg back the leaders include Francisco Mancebo, Oscar Pereiro, Jorg Jaksche and Stefano Garzelli
1340: With every pedal turn, the peloton gets thinner and thinner. Riders are dropping off the back all the time as they go up the Cormet-de-Roseland - the first category one climb of the day. The latest duo to be struggling are sprinters Thor Hushovd and Tom Boonen.
1333: At the moment the sun is shining on the riders, with stunning views of the French Alps just ahead of them. Long before the really nasty climbs begin, the crowds are already building. French favourite Moreau is getting plenty of road-side cheers at the front of the peloton.
1315: The riders come through the feeding station - with the leaders 8mins 30s clear. The break in action sees Gerrit Glomser of the Lampre team retire.
1250: The Credit Agricole team of Christophe Moreau have given Armstrong's Discovery team a bit of a breather by heading up the chase on the leaders. It cuts the leading seven's advantage from 11 minutes down to nine.
1231: Yellow jersey wearer Jens Voigt hardly sounded confident of holding on to the race lead ahead of the stage. He told reporters ahead of the start: "I am a mediocre sprinter, a bad climber and an okay time trailer. But really, I am not very good at anything."
1216: The first sprint of the day goes to Bortolami. The results are:
1. Gianluca Bortolami (Lam) 6pts
2. Mauro Facci (Fas) 4pts
3. Yuriy Krivtsov (A2R) 2pts
1212: 33 riders in the peloton were tested by Tour organisers at their hotels on Tuesday morning. The riders were from the Lampre, Ag2R, CSC and Discovery Channel teams. Only Evgeni Petrov failed to get the all clear.
1201: We now have seven leaders of the 10th stage. Krivtsov, Posthuma and Brochard are joined by Mauro Facci, Luis Sanchez, Gianluca Bortolami and Inaki Isasi. Their advantage is an already ample six minutes. But race leader Jens Voigt won't be too bothered. None of the leading line-up are a major threat.
1147: Already the trio of Krivtsov, Posthuma and Brochard have a lead of 1m 20s to the pack containing the major contenders.
1140: The main team leaders will be doing their utmost to make their mark on this stage.
1136: The stage finally starts in earnest and attacks begin immediately. As a result a break of three riders immediately emerges: Yuriy Krivtsov, Joost Posthuma and Laurent Brochard. But neither man is a major danger to the yellow jersey.
1127: Grenoble, where today's stage was supposed to start (before fears over farmers protesting which seems to be happening anyway) is the capital of the French Alps and the sign the big ascents are on their way.
1118: The racing is just moments away from starting. All of the riders are now lined up on the official startline in Brignoud but there is a slight delay due to some protests.
1103: The racers have been reduced to 174 (from a start of 189) after five riders withdrew during the ninth stage - Dave Zabriskie, Jose Angel Gomez, Igor Gonzalez de Galdeano, Jaan Kirsipuu and Luciano Pagliarini.
1039: The peloton is gently meandering its way through the neutral zone before the real racing begins.
1030 BST: The cyclists are moments away from rolling out of Brignoud. The stage had been due to start in Grenoble but was moved to Brignoud because of fears of a farmers' strike. The peloton is down a man today after Evgeni Petrov was thrown out of the race for failing a blood test.