An executive for UBS AG, Switzerland's largest bank, said its country's laws prevent it from turning over most of the 52,000 customer identities being sought by the US in a lawsuit that seeks to crack down on tax evaders.

UBS agreed on Feb 19 to pay $780 million and disclose some client names to avoid prosecution for helping wealthy Americans avoid taxes. The bank has agreed to turn over about 300 names, said Senator Carl Levin, chairman of a Senate panel that held a hearing in Washington yesterday on offshore tax havens.

UBS executive Mark Branson said at the hearing that bank officials "believe that UBS has now complied with the summons to the fullest extent possible without subjecting its employees to criminal prosecution in Switzerland" under bank-secrecy laws. Branson is chief financial officer of global wealth management at UBS.