May 29 (Bloomberg) -- A former UBS AG banker has agreed to plead guilty to helping a billionaire real-estate mogul evade U.S. taxes on money stashed in bank accounts in Switzerland and Liechtenstein, the Justice Department said.

Bradley Birkenfeld, who worked in the firm's private banking division, scheduled a ``change of plea'' hearing for June 9 in federal court in Fort Lauderdale, Florida, according to court papers. The filing notes that the judge ``will ask for a full confession.''

Birkenfeld, who worked at UBS from 2001 to 2006, had pleaded not guilty earlier this month after he was indicted with Mario Staggl of Liechtenstein. Staggl is a fugitive, prosecutors have said.

The case is part of a growing U.S. investigation into whether UBS helped clients avoid paying taxes. The probe has added to the trouble swirling around the bank, which has also been hit hard by the subprime loan crisis.

By changing his plea, Birkenfeld is signaling he will help prosecutors and identify other UBS customers who shielded assets to escape paying income taxes, said Eileen O'Connor, former head of the Justice Department's tax division.

``He's decided to cooperate,'' said O'Connor, now a partner at the Pillsbury Winthrop Shaw Pittman law firm in Washington.

The indictment, unsealed May 13, alleges Birkenfeld and Staggl attempted to sidestep rules in a U.S.-Switzerland tax treaty that requires information to be exchanged on some financial transactions. The pair -- and others not identified by prosecutors -- allegedly traveled to the U.S. to pitch their schemes.

Billionaire Identified

Birkenfeld's attorney, Peter Raben, didn't return a call and e-mail seeking comment. UBS spokesman Doug Morris declined to comment, as did Alicia Valle, a spokeswoman for the Justice Department in Florida.

The billionaire beneficiary, unnamed in court papers except for his initials, has been identified as Igor Olenicoff, founder of Olen Properties Corp. He pleaded guilty in December to a charge of filing a false tax return and agreed to pay $52 million in back taxes, penalties and interest.

Olenicoff was ranked 236 on the Forbes Magazine list of the 400 wealthiest Americans this year, with a net worth of $1.7 billion. He was sentenced to probation, 120 hours of community service and a $3,500 fine in April.

Birkenfeld, 43, and Staggl helped Olenicoff evade U.S. income taxes on about $200 million in assets, prosecutors said.

The case is U.S. v. Bradley Birkenfeld and Mario Staggl, 08- 60099, U.S. District Court for the Southern District of Florida, Fort Lauderdale.

To contact the reporters on this story: Ryan J. Donmoyer in Washington at rdonmoyer@bloomberg.net; Robert Schmidt in Washington at Rschmidt5@bloomberg.net

Last Updated: May 29, 2008 17:22 EDT