Italian automaker Fiat SpA is nearing a deal to buy the U.S. Treasury's remaining 6 percent stake in Chrysler Group LLC and could pay more than $500 million, the Wall Street Journal reported on Thursday.

The deal is supposed to be announced Friday by President Barack Obama during a visit to a Chrysler plant in Toledo, Ohio, the Journal reported, citing three people familiar with the matter.

As part of the deal, the Treasury will also transfer to Fiat an option to purchase all of the 45.7 percent stake owned by the United Auto Workers union's healthcare trust fund, sources told the Journal.

Fiat and the Treasury could not be immediately reached for comment.

(Reporting by Deepa Seetharaman; Editing by Steve Orlofsky)