U.S. authorities seem to tell court its insights into the details are murky. The number of undeclared Swiss-based bank accounts held at UBS by Americans falls "far short" of the 52,000 the Zurich-based bank had been bandying about in its spat with U.S. authorities over its alleged complicity in helping some of those clients get out of paying taxes in the U.S.

"The number of undisclosed accounts that the IRS has discovered through 'alternative means' falls far short of the 52,000 accounts that UBS has identified," says a U.S. Department of Justice filing. "There is no dispute that the vast bulk of information sought in this summons is not in the IRS's possession."

Sinker

The filing was a response to a Miami-based U.S. federal court's order that U.S. authorities respond to UBS' request for details of the accounts in question.

Though the Justice Department didn't say how many accounts it had a bead on, it affirmed that "the vast bulk of information sought in this summons is not in the IRS's possession" -- a hint that without UBS' cooperation, it's case against it may be in jeopardy.

UBS, which earlier this year agreed to pay a fine of $780 million to U.S. authorities for urging a few hundred wealthy U.S. clients to open accounts in Switzerland in order to keep income hidden from the IRS, is now digging in its heels. Having provided information on those accounts, it says it has no obligation to betray the privacy of other clients (and break Swiss privacy laws) in aid of what it characterizes as a fishing expedition by U.S. authorities.

Late last year, Raoul Weil, head of UBS' wealth-management and business-banking segments, left the bank following his indictment by a Florida grand jury for conspiring to defraud the U.S. government by hiding assets secret Swiss bank accounts. -FWR

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