Calpine Corp., the largest U.S. issuer of junk bonds in 2004, said Wednesday it will sell as many as eight power stations and idle money-losing plants to accelerate $3 billion in debt reduction.

Beleaguered Calpine Corp., a once-highflying power producer that has been selling assets to reduce debt, has confirmed new troubles: The company said Thursday that it was unable to withdraw $400 ...