Russian state prosecutors on Thursday formally charged top U.S. investor Michael Calvey, the founder of the Baring Vostok private equity group, with fraud, hours before Washington accused Moscow of denying its diplomats access to him.

Calvey was first detained last week along with three other executives from his fund after investigators accused him and others of embezzling 2.5 billion roubles ($38.17 million).

Calvey denies the allegations against him, saying the case is being used to apply pressure on him in a business dispute over a Russian bank in which he is a shareholder.