Floyd Landis claims the yellow jersey after finishing third in the time-trial - the penultimate stage of the Tour.
Honchar gave another awesome display of time-trialing
The American started 30 seconds behind Oscar Pereiro but transformed that deficit into a 59-second lead going into Sunday's final stage into Paris.
Ukrainian Serhiy Honchar took his second time-trial win of this year's Tour with another awesome display.
Andreas Kloden finished second to lift the German into third overall, knocking Carlos Sastre out of a podium place.
LATEST UPDATES (all times BST)
By Bryn Palmer and Martin Gough
Result of time-trial:
1. Serhiy Honchar (Ukr/T-Mobile) 1:07:46
2. Andreas Kloeden (Ger/T-Mobile) 1:08:26
3. Floyd Landis (USA/Phonak ) 1:08:56
4. Oscar Pereiro (Spa/Caisse) 1:10:25
5. Sebastian Lang (Ger/Gerolsteiner) 1:11:03
1624: Oscar Pereiro comes home fourth after a commendable time-trial, but he loses the yellow jersey to Floyd Landis, who will enjoy a 59-second lead going into Paris on Sunday.
1619: Only Carlos Sastre and Oscar Pereiro are out on the course now, as we wait to discover how much of an overall lead Landis will enjoy going into Sunday's final stage into Paris.
1617: Landis comes home in 1:08:56, 30 seconds behind Kloden, but enough to give him the overall lead.
1614: Landis passes the third check-point 1:08 down on Honchar, but on course to reclaim the yellow jersey.
1612: Kloden completes an excellent time-trial, coming home second, 40 seconds behind Honchar. It is likely to propel the German into the top three overall, with Carlos Sastre struggling.
1604: Andreas Kloden is also going well, only seven seconds behind Landis after 34km. He has narrowed his deficit on Carlos Sastre, down to third overall at this stage, to two seconds, threatening the Spaniard's podium place.
1558: Oscar Pereiro is now nearly a minute down on Landis as he passes through the second check-point 1:22 down on Honchar, fourth fastest. That equates to a 27-second lead overall for Landis at this stage.
1553: Landis is staying in his prone, elbows-on-the-handlebars position whereas Pereiro is mostly up out of the saddle as he battles to stay ahead of the American overall.
1551: Landis appears to be suffering a bit, passing the second check-point 26 seconds adrift of Honchar, having been a second quicker through the first, but still the second quickest at 41:45 after 34km.
1549: The wind is starting to pick up a bit as Landis and Pereiro approach the second time check. Has the American maintained his early form?
1543: Damiano Cunego puts in an exceptional performance to come in sixth fastest so far in 1:11:30, narrowly ahead of Scot David Millar (1:11:46), to extend his lead over Marcus Fothen for the white jersey from five to 36 seconds.
1540: Oscar Pereiro is putting up a huge fight to keep hold of the yellow jersey, but Landis appears to be inching closer to the leader, with the overall deficit now around 10 seconds as they approach the second check-point.
1535: Race leader Oscar Pereiro crosses the first check-point after 16.5km 10 seconds behind Landis, so the American is 20 seconds down in the battle for the yellow jersey with 40km to go.
1531: Carlos Sastre is already 1:04 down on Landis at the first time check.
1528: Confirmation that Floyd Landis is in good shape. The American is a second faster than Honchar at the first check-point, blitzing the first 16.5km in 19:46.
1526: Andreas Kloden, who started fourth overall, 2:32 behind Pereiro, is the closest challenger to Serhiy Honchar at the first time check, 10 seconds behind the Ukrainian.
1516: Italian Damiano Cunego is going superbly in his bid to hold onto the white jersey. He has maintained his pace at the 34km mark, third overall and 50 seconds better than Marcus Fothen.
1514: Oscar Pareiro, sporting the leader's maillot jaune, sets off for the most important time-trial of his life.
1511: Spaniard Carlos Sastre, 12 seconds behind Pareiro and 18 ahead of Landis, heads down the ramp to begin his attempt.
1509: American Floyd Landis, favourite for overall victory now, starts his time-trial.
1502: We're down to the last five now. Australian Cadel Evans, 3:11 behind Pareiro beforehand, sets off.
1500: Floyd Landis is fancied to overturn his 30-second deficit on yellow jersey holder Oscar Pereiro on account of his previous time-trial displays. On stage seven in Rennes this year, he was 1 minute 10 seconds ahead of Carlos Sastre (18 seconds ahead of him overall), and 1 min 40 secs ahead of Pereiro. Last year, in the final time-trial at St Etienne, the gaps were 1 min 8 secs and 1 min 32 secs respectively.
1455: Damiano Cunego, currently in the white jersey for the Tour's best young rider, is making a good fist of keeping it. He is third at the first check-point, 46 seconds behind Honchar, but more importantly 12 seconds better than his nearest rival Marcus Fothen.
1451: Frenchman Christophe Moreau sets off, aiming to overhaul compatriot Cyril Dessel, 7th overall, as the hosts' top performer. Moreau was 1:21 adrift of Dessel before the start.
1448: The Tour has never ahad a tighter three-way finish than this, with the top three within 30 seconds of each other before they set off contre la montre today.
1445: We are getting towards the business end of the day now. Franck Schleck, 11th in the overall classification, sets off, with just the top 10 to go now. Oscar Pereiro, the current leader, goes off in half an hour.
1423: That slightly frightening combination of red polka dots, orange helmet and blond beard means King of the Mountains Michael Rasmussen is underway. In the final time-trail last year he crashed three times, ruining his chances of a podium finish in Paris.
1418: Yellow jersey Oscar Pereiro is already warming up on the stationary bike at the start, with almost an hour to go before his scheduled start. The leading riders will have scouted the course this morning, although the weather has dried up since.
1410: As expected, Serhiy Honchar is easily the fastest so far, bettering Lang's previous best by 3:18 as he steams over the line with those familiar rolling shoulders. The world time-trial champion six years ago won the other long time-trial in this race, stage seven into Rennes, and will take some bettering here. Robbie Hunter can pack his bags now, by the way.
1406: Britain's David Millar comes across the finish line with a grimace on his face, a little wobble over the line and fifth fastest so far in 1:11:46.
1400: Riders who take more than 125% of the winner's time today face an agonising elimination just a stage away from Paris. If there is not a massive improvement on Lang's time, the cutt-off appears to be around 1:28:00. South Africa's Robbie Hunter is slowest so far in 1:25:54 so he will be biting his nails watching Landis in an hour's time.
1357: The imposing Axel Merckx starts but he will be no help to his Phonak team leader today. Drafting - where one rider tucks in behind another to escape the wind - is expressly prohibited in this race against the clock.
1353: George Hincapie rolls down the ramp, almost at the end of a disappointing Tour for the big American, who is more than an hour down in the general classification after wearing yellow early in the race.
1349: Sebastian Lang posts the best time of the day after covering the course at an average of 48.1 km/h.
1346: Serhiy Honchar has gone through the second check a massive 2 mins 8 secs ahead of Lang, the previous best. It looks like the Ukrainian is in the same form that saw him take yellow in the first time-trial of this race.
1340: David Millar is sixth fastest of the 81 riders to complete 34 of the 57km, 25 seconds adrift of the best split-time at the second check.
1335: Zabriske, a noted time-trial specialist, lives up to his reputation by taking the lead with a time of 1:11:20.
1330: American David Zabriskie is challenging for the lead. He is just a second adrift of Ekimov as he approaches the final 5km.
1325: Serhiy Honchar, the runaway winner of the stage seven time-trial, has started at a furious lick. He is already 42 seconds quicker than anyone else at the first checkpoint after 16.5km.
1307: Viatceslav Ekimov, the oldest man in the race, sets the new best time of 1:11:27, two seconds quicker than Grabsch.
1305: David Millar did not appear optimistic about his chances before today's time-trial. "I am not firing at my best," he said. "I am not getting better anymore, I am getting worse. I am not going to get a result."
1300: German Sebastian Lang has started strongly, going through the first check-point after 16.5km at Monchanin-le-Haut 14 seconds quicker than Grabsch.
1255: Britain's David Millar, a good time-trialist in the past, sets off from Le Creusot. The Scot is 61st of the 141 riders left in the race, more than two hours adrift of the maillot jaune holder Oscar Pareiro.
1243: Viatceslav Ekimov, the oldest man in the race at 40, is going well. At the second checkpoint at 34km, he is only eight seconds behind Grabsch's split-time.
1237: Gustaf Larsson finishes 37 seconds adrift of Grabsch, but moves into second place for the time being.
1230: German Bert Grabsch, a Phonak team-mate of Floyd Landis, takes a whopping 2:37 out of Vansummeren's best time, with Swede Gustaf Larsson also finishing fast.
1220: We have another new leader. Belgian Johan Vansummeren, of the Davitamon-Lotto team, takes 49 seconds off Mugerli's time, coming home in 1:14:06.
1214: Wiggins is now down to third as Swiss Michael Albasini comes home in 1:15:07, 13 seconds behind Mugerli.
1208: Wiggins' moment in the sun is short-lived as Slovenian Matej Mugerli beats the Briton's time by 27 seconds.
1202: Wiggins' time shouldn't last long. German Bert Grabsch, a Phonak team-mate of Floyd Landis, is more than a minute ahead of Johan Vansummeren, who was in turn a minute faster than Wiggins, at the second checkpoint.
1158: Bradley Wiggins is the quickest of the first 14 riders to finish, covering the 57km to Montceau-les-Mines in 1:15:21. How long will his time last?
1153: Belgian Johan Vansummeren is the fastest rider out on the course, almost a minute quicker than Wiggins after 34km.
1151: Bradley Wiggins is the fastest rider to pass through Villa-Sirot, the third checkpoint after 51.5km, 5.5km from the finish. Can the Briton hold on to set the new fastest time?
1145: Christophe Mengin, of the Francaise des Jeux team, is the new leader, beating Pozzato's time by seven seconds.
1142: Italian Filippo Pozzato takes 25 seconds off Hernandez' time to finish in 1:15:38, but Frenchman Christophe Mengin is a second quicker with 5.5km left.
1138: Vansevenant's effort is immediately put into perspective as Gert Steegmans comes in nearly three minutes quicker, before Aitor Hernandez surpasses that to post the new best time of 1:16:02.
1134: Belgian Wim Vansevenant, the first man to go, sets the target time of one hour 19 minutes and 11 seconds as he arrives at Montceau-les-Mines after completing the 57km.
1130: Frenchman Florent Brard pips Wiggins' second split-time after 34km by five seconds.
1125: Britain's Olympic champion Bradley Wiggins is burning up the course, and takes 10 seconds off Pozzato's split-time at the second checkpoint. Wiggins has covered 34 of the 57km in 45:39.
1116: Italian Filippo Pozzato, of the Quickstep team, was only fourth fastest at the first checkpoint but steps up the pace to beat the second split-time of Hernandez by three seconds in 45:49.
1112: Frenchman Florent Brard sets a new best first split-time of 21:09 in Montchanin-le-Haut.
1108: Aitor Hernandez is more than two minutes quicker than the first three riders at the second checkpoint, completing 34km in 45:52.
1102: Britain's Bradley Wiggins is the second quickest of the 15 riders to have passed through the first checkpoint so far, five seconds adrift of Hernandez in 21:18.
1047: The second split-time will come near Montcenis after 34 of the 57km.
1043: Spaniard Aitor Hernandez, the fourth rider to go, sets a new split-time target of 21:14, 1:30 quicker than the previous best of Gert Steegmans.
1038: Wim Vansevenant passes through the first split-time checkpoint after 16.5km at Montchanin-le-Haut in 22 minutes and 53 seconds.
1031: There are 141 riders left in the Tour, and those at the bottom of the overall standings have been leaving at two-minute intervals.
1017: Another Belgian Davitamon-Lotto rider, Gert Steegmans, normally Robbie McEwen's lead-out man for the sprint finishes, is the second rider to head off.
1015: Belgian Wim Vansevenant, the "lanterne rouge" of the Tour as the last man in the general classification, leaves Le Creusot.