The charge against Bradley Birkenfeld -- which could affect an ongoing U.S. investigation of UBS's conduct in relation to services it provided to U.S. clients from 2000 through 2007 -- was contained in a grand jury indictment unsealed last month.

It charged Birkenfeld with conspiring to defraud the United States by helping the unidentified U.S. billionaire create bogus corporations and other entities to conceal the ownership of hidden offshore assets.

(Reporting by Kathy Skipper and Tom Brown; Editing by Michael Christie and Gerald E. McCormick)