Two people familiar with the case told The Associated Press that Pettitte was in Washington last week to meet with prosecutors. The people spoke on condition of anonymity.
The two trained together for years. Pettitte has acknowledged taking human growth hormone and told congressional investigators that Clemens informed him nearly a decade ago that he used HGH.
Prosecutors are weighing whether to bring perjury charges against Clemens for denying under oath to Congress that he took performance-enhancing substances.
Lawyers for Pettitte declined to comment.