A source close to Sen. Rand Paul (R-KY) said the senator may put a hold on Janet Yellen’s nomination to chair the Federal Reserve, CNBC reported Friday.

Paul wants his Fed transparency bill, which would mandate a complete audit of the Federal Reserve, to come to a vote and has informed Senate leadership of his intentions to formally put the hold in place next week, the source told CNBC.

A request for comment was not immediately returned by Paul’s office.

This post has been updated.