A top UBS AG executive told a U.S. lawmakers that the Swiss bank regrets breaking U.S. tax laws, but criticized U.S. authorities' efforts to obtain information on thousands of bank accounts suspected of being used by American tax dodgers.

"We deeply regret our breaches of U.S. laws," UBS' Mark Branson told a Senate subcommittee hearing into a crackdown on offshore tax havens that has called into question Switzerland's cherished tradition of banking secrecy.

Branson called for a diplomatic resolution of U.S. government efforts to get information from UBS on as many as 52,000 undisclosed accounts sought in a civil lawsuit filed against the bank by the U.S. Internal Revenue Service.

"UBS believes the dispute should be resolved through diplomatic discussions" between the governments of Switzerland and the United States, Branson said, adding that the bank believes it has complied as much as possible with the lawsuit.

"The IRS is attempting to resolve this diplomatic dispute in a courtroom, which is neither productive, nor proper," he said.