Former WorldCom chief financial officer Scott D. Sullivan pleaded guilty Tuesday to charges stemming from the multibillion-dollar accounting scandal at the telecommunications giant and agreed to cooperate with prosecutors.

The change of plea came as federal prosecutors filed charges against former chief executive Bernard Ebbers for his role in the nation's largest accounting scandal.

In an indictment filed Tuesday in U.S. District Court in Manhattan, Ebbers was charged with conspiracy to commit securities fraud, securities fraud and falsely filing with the Securities and Exchange Commission.

Sullivan said in court that he had signed a deal with prosecutors agreeing to cooperate, with the possibility that substantial cooperation could decrease any potential sentence.

The judge told him that the potential prison term stemming from the charges of conspiracy to commit securities fraud, securities fraud and false filing with the SEC was 25 years in prison.