Cadel Evans is all but certain to become Australia's first Tour de France winner after a stunning time trial-victory in the suburbs of Grenoble.
Evans recorded a time of 55 minutes 40 seconds to take the yellow jersey from Andy Schleck before Sunday's largely ceremonial final stage in Paris.
Germany's Tony Martin won the time-trial from Evans, who moved 1:34 ahead of Schleck in the overall standings.
Schleck began the day with a 53-second lead in the general classification.
The Luxembourger is destined for a third consecutive second place in the Tour after the aggression that secured his stage win over the Galibier on Thursday appeared to catch up with him.
Evans, a general classification runner-up in 2008 and 2009, was visibly emotional as he was presented with the yellow jersey.
In the absence of Alberto Contador in 2008, the Australian was widely expected to land his first Grand Tour title but was foiled by Carlos Sastre.
"Fortunately this year, we're close to Paris", Evans added after Saturday's dramatic stage.
"This is the result of a lot of planning and experience. This is my seventh Tour de France and not having bad luck has been good to me.
"In 2008 I suffered so much with my injuries it was the hardest Tour."
Back on the flat in this year's decisive stage, the time-trial specialist, took revenge in ruthless style.
The 34-year-old soon eliminated the four-second gap that had separated him from Schleck's older brother Frank before powering away to register a stage time 2:31 superior to Andy.
The Schlecks will have the small consolation of being the first set of brothers to feature in the same Tour de France podium after Frank successfully defended his third place in the overall standings.
But barring a freak accident or illness Evans, the road race world champion in 2009, will be crowned Tour de France winner on Sunday.
The final 95km run into Paris is traditionally not contested by the general classification contenders as the sprinters take centre stage on the Champs-Elysees.
"I really can't quite believe it right now. I have been concentrating on this one event for so long," said Evans, who came within seven seconds of decorating his success with a stage win.
Tour de France director Christian Prudhomme added: "This is the victory of a complete rider. It is the consecration of a career."
Thomas Voeckler, who held yellow for 10 days before Friday, is fourth in the overall standings after coming 13th on the day with a typically gritty ride.
The Frenchman is 37 seconds ahead of Contador, who came third on the day, 1:06 off Tony Martin's winning stage time.
After starting in damp conditions earlier in the day, Fabian Cancellara, the world and Olympic time-trial champion and many people's favourite for the stage, was eighth fastest.
STAGE 20 RESULT:
1. Tony Martin (Germany / HTC - Highroad) 55 minutes 33 seconds
2. Cadel Evans (Australia / BMC Racing) +7"
3. Alberto Contador (Spain / Saxo Bank) +1:06"
4. Thomas De Gendt (Belgium / Vacansoleil) +1:29"
5. Richie Porte (Australia / Saxo Bank) +1:30"
6. Jean Christophe Peraud (France / AG2R) +1:33"
7. Samuel Sanchez (Spain / Euskaltel) +1:37"
8. Fabian Cancellara (Switzerland / Leopard) +1:42"
9. Peter Velits (Slovakia / HTC - Highroad) +2:03"
10. Rein Taaramaee (Estonia / Cofidis) at same time
1 Cadel Evans (Aus/BMC) 83hrs 45mins 20secs,
2 Andy Schleck (Lux/Leopard Trek) +1:34
3 Frank Schleck (Lux/Leopard Trek) +2:30
4 Thomas Voeckler (Fra/Europcar) +3:20
5 Alberto Contador Velasco (Spa/Saxo Bank) +3:57
6 Samuel Sanchez Gonzalez (Spa/Euskaltel-Euskadi) +4.55
7 Damiano Cunego (Ita/Lampre) +6:05
8 Ivan Basso (Ita/Liquigas) +7:23
9 Thomas Danielson (U.S.Garmin-Cervelo) +8:15
10 Jean-Christophe Peraud (Fra/AG2R) +10:11