Lance Armstrong has identified Ivan Basso as the main rival in his efforts to win a record sixth Tour de France.
Armstrong leads Basso across the line at Plateau de Beille
The American set out his stall in two Pyrenean stages during which he made up more than five minutes on Jan Ullrich and Tyler Hamilton pulled out.
He is 22 seconds off Thomas Voeckler's lead and 1:17 ahead of Basso.
"Ivan's riding great and could be the future of the Tour, but anyone within three minutes is still a threat," Armstrong said after winning stage 13.
Armstrong sprinted across the line at the end of the hors category climb to Plateau de Beille on Sunday to deny Basso two successive stage wins.
The roles had been reversed 24 hours earlier when the Italian led Armstrong home.
"It was one of the most difficult stages in the Tour," Armstrong said of the 205.5km 13th stage from Lannemezan, which took in seven climbs.
And he is keeping his feet on the ground despite the success.
"As I always say, the Tour finishes in Paris. Ivan is very, very strong. I'm impressed and it was not possible to drop him," he added.
"He was strong and I couldn't shake him but we worked well together.
"It was important we worked together as it was in our best interests to put time in on the rivals behind.
"I wanted to win. It was important to win and it was a good day. I felt better on the bike and we'll see if we can carry it into the Alps."
Armstrong reserved special praise for Voeckler, who put in the ride of his life to hold onto the lead.
The Frenchman, cheered on by the home crowd, crossed the line 4:42 down to ensure he will enjoy an eighth day in yellow from Carcassonne to Nimes on Sunday.
"Getting dropped, coming back, getting dropped, coming back - he's so tough and absolutely deserves it," Armstrong said.