Prosecutors are seeking about $1 billion to resolve a long-standing probe into Johnson & Johnson's marketing of its Risperdal anti-psychotic medicine, the Wall Street Journal said on Thursday, citing sources familiar with the matter.

Johnson & Johnson in a regulatory filing earlier this week said it had set aside an unspecified amount of money for a potential settlement of the probe into whether the company promoted Risperdal for unapproved uses.

Prosecutors are pushing J&J to reach a settlement soon, the Journal said on Thursday, citing one source.

J&J officials could not immediately be reached for comment.

A spokeswoman for the Attorney's Office in Philadelphia declined to comment on the report.

(Reporting by Ransdell Pierson; Editing by Richard Chang)