U.S. Postal covered the 69 kilometers from Joinville to Saint-Dizier in 1:18.27 hours, an astonishing clip of 52.77 kph, the second-fastest speed in any team trial in Tour history.
Most important, Armstrong gained 30 seconds on his strongest rival, Joseba Beloki, whose ONCE team finished second. The American now leads the Spaniard by 33 seconds.
The 31-year-old Armstrong also gained 43 seconds on former Tour winner Jan Ullrich, who came in third with his Bianchi team, and put Colombian Santiago Botero of Team Telekom 1 minute 30 seconds behind him.
Armstrong's U.S. teammate Victor Hugo Pena became the first rider of Colombian nationality to wear the Tour leader's yellow jersey. He leads Armstrong by one second and will likely keep the lead until the race heads into the Alps on Saturday.
"I always watched the Tour back home as a boy," a beaming Pena said. "It's always been a dream to wear the yellow jersey."
Armstrong was not as delighted after the race, telling France 2 television that he did not feel strong during the stage. However, Pena jokingly described the 31-year-old Texas native as "my best teammate today."
Although the performance of Armstrong's team put his challengers on notice that he remains the strong favorite to win a record- equaling fifth consecutive Tour de France, seven formidable mountain stages lay ahead.
On Saturday, the Tour heads into the Alps, and Armstrong will likely take over the yellow jersey from his teammate. After that, it will be up to him and his team to defend it until they reach the finish line in Paris on July 27.
Thursday's fifth stage, 196.5 kilometers from Troyes to Nevers, will give the riders an opportunity to rest from Wednesday's exertions and again showcase sprinters such as Italian Alessandro Petacchi, who has already taken two Tour stages.
Stage 4 results, top 10 (team time trial, Joinville - Saint-Dizier, 69 km)
1. US Postal 1hr 18mins 27secs (average speed 52.77km/h)
2. ONCE at 30
3. Bianchi 43
4. ibanesto.com 1:05
5. Quick Step 1:23
6. Telekom 1:30
7. Vini Caldirola 1:32
8. Credit Agricole 1:32
9. AG2R 1:38
10. CSC 1:45
Stage 4: Overall standings, top 15
1. Victor Hugo Pena (COL/USP) 13 hr 44min 44sec
2. Lance Armstrong (USA/USP) at 0:01sec
3. Viacheslav Ekimov (RUS/USP) 0:05.
4. George Hincapie (USA/USP) 0:05.
5. Jose Luis Rubiera (SPA/USP) 0:23.
6. Roberto Heras (SPA/USP) 0:27.
7. Pavel Padrnos (CZE/USP) 0:27.
8. Floyd Landis (USA/USP) 0:28.
9. Joseba Beloki (SPA/ONC) 0:33.
10. Joerg Jaksche (GER/ONC) 0:38.
11. Manuel Beltran (SPA/USP) 0:39.
12. Jan Ullrich (GER/BIA) 0:39.
13. Isidro Nozal (SPA/ONC) 0:44.
14. Angel Vicioso (SPA/ONC) 0:51.
15. Tobias Steinhauser (GER/BIA) 0:51.