Reigning champion Armstrong produced a determined performance on the Alpe d'Huez to move into fourth place overall after the first mountain stage.

But Ullrich moved up to seventh after finishing second behind the US Postal rider on Tuesday.

And the German believes he is capable of more in the near future.

"It was only the first of the mountain stages," the Telekom rider told the German Bild daily.

"I rode well in the final stage. I took everyone, except Lance. I don't know what I should do.

"I'm in super form, maybe Lance will have a setback. At least I didn't lose as much ground as I did last year on the first mountain stage."

The 27-year-old highlighted his new high-tech bike as a factor which could prove decisive in the four remaining mountain stages.

"I'm comfortable on the bike and I have a good feeling, the most important thing is that it's one kilo lighter," said Ullrich.

The man both Ullrich and Armstrong are chasing is Frenchman Francois Simon, who wears the yellow jersey going into Wednesday's 11th stage, a 32km mountain time trial.