UBS says it will not provide the names of any more American clients to the United States authorities in a fight over secrecy and tax avoidance.
Appearing before a Senate subcommittee on Wednesday, UBS senior wealth management executive Mark Branson said the bank "has now done all that it can do to cooperate" with the Internal Revenue Service (IRS) request without violating Swiss criminal laws.
"We respectfully submit that the IRS is attempting to resolve this diplomatic dispute in a courtroom, which is neither productive nor appropriate," he said. "UBS cannot disclose information to the IRS that would put its employees at serious risk of criminal prosecution under Swiss law."
Switzerland's biggest bank has accepted responsibility for helping thousands of Americans hide assets from the US government, but is not giving the IRS the names of all US citizens who maintain secret accounts with the bank.
Branson added that banking secrecy is a value treasured by the Swiss just as freedom and democracy are treasured by Americans.
A Senator questioning Branson retorted that banking secrecy as practiced in the UBS case was no value but a "conspiracy" to break US law.
UBS already has paid hefty fines and turned over the names of about 250 US clients, but the IRS wants the identities of 48,000 wealthy Americans who maintain secret accounts with bank. That is slightly fewer than the 52,000 names originally requested.