The stage was led for most of the way by the three-man breakaway of Mickael Rasmussen, of Rabobank, CSC rider Jens Voigt and La Boulangere's Sylvain Chavanel.
However Chavanel was dropped on one of the last climbs of the day, and Rasmussen and Voigt were caught by Armstrong, his US Postal teammate Jose Azedvedo and Basso just after they began the 15.9km climb to the Plateau.
From then on, it was all about the front trio.
Azevedo had done his job and dropped back, while Armstrong and Basso forged ahead on their own as the sorry figure of Ullrich clung on to go round every bend.
The German's chances of even staging a challenge now look remote, although Ullrich remained strangely upbeat.
"I felt a bit better than yesterday, although I'm still having muscle problems. Hopefully, I can improve my performance in the Alps.
"You could say that Armstrong is unbeatable, but there are a lot of hard stages between now and Paris, and I'll be fighting all the way."
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