(Reuters) -U.S. federal prosecutors have filed criminal charges against George Santos, the embattled Republican U.S. congressman who has admitted to lying about his resume but defied calls to step down, CNN reported on Tuesday, citing three sources.

Santos is expected to appear as soon as Wednesday in federal court in New York's Eastern District, where charges have been filed under seal, CNN reported.

A spokesman for the U.S. Attorney's office for the Eastern District of New York declined to comment. Santos' office did not immediately respond to a request for comment.

CNN reported that the exact nature of the charges against Santos were not immediately clear.

However, federal prosecutors have been examining false statement allegations in Santos' campaign filings.

In March, the U.S. House of Representatives Ethics Committee launched a probe looking at a variety of concerns, including whether Santos engaged in illegal activity over his 2022 campaign, failed to properly disclose information required on House statements, and violated federal laws concerning his role in a financial firm.

Santos' office, through his congressional Twitter account, has previously said he is cooperating with the House Ethics Committee's investigation.

(Reporting by Rami Ayyub, Sarah N. Lynch and Luc Cohen; Editing by Leslie Adler and Bill Berkrot)