Toshiba expects a Chapter 11 filing for Westinghouse would expand charges related to the U.S. unit in the current financial year to around 1 trillion yen (7.21 billion pounds) from publicly flagged estimates of 712.5 billion yen, the sources told Reuters.

The sources declined to be identified as they were not authorised to speak to media on the matter.

Toshiba said on Friday it was not appropriate to comment prematurely.

"Whether or not Westinghouse files for Chapter 11 is ultimately a decision for its board, and must take into account the various interests of all of its stakeholders, including Toshiba and its creditors," it said in a statement.

Toshiba is seeking to limit future losses at Westinghouse with a Chapter 11 filing. Westinghouse has been plagued by huge cost overruns at two U.S. nuclear projects.

(Reporting by Taro Fuse; Writing by Makiko Yamazaki; Editing by Edwina Gibbs)