Speculation had mounted that the Danish oufit could bring in a new rider to replace Giro winner Basso, who failed to regain the trust of Riis after being implicated in the Operacion Puerto doping scandal.
But the 1996 Tour de France winner told Danish daily B.T: "I don't want to spend more money than what has already been laid out."
"I have great respect for the 2006 achievements of Sastre. He will be our leader. Frank Schleck is a man for the future."
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Riis admitted a victory in next year's Tour de France would become "more difficult", though insisted "there is life besides the Tour."
Sastre finished fourth in both the Tour de France and the Vuelta a Espana this year, though had originally expected to ride the Tour in support of Ivan Basso. But when the Spanish blood doping scandal broke just 24 hours before the start of the race, the 31-year-old was left as CSC's main hope in the general classification.
"I couldn't have been better prepared than I was then, but I will probably choose to prepare differently for 2007, because it will be an entirely new race for me yet again," Sastre revealed.
"It's always tough in the Alps regardless of which other climbs you have to do, but I believe the Alps might decide the race for some rider in 2007.
"There are also two long time-trials, which will be crucial as well and other than that two important stages in the Pyrenees. Especially the final mountain stage following the second rest day - the one finishing on the Col d'Aubisque. It will be tough," he added.
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