Cyrill Sele, a Vaduz, Liechtenstein-based spokesman for Liechtensteinische Landesbank AG, said it sent statistical data to the U.S. A man who answered the phone Oct. 20 at NZB said it is closing and has only a few employees.

Zuercher Kantonalbank spokesman Urs Ackermann said the bank was informed in September of the U.S. investigation. A spokesman for Mizrahi Bank had no immediate comment.

The UBS turnover of 4,450 names, in the face of Swiss laws barring most disclosures of client data, set a precedent for the current talks. The U.S. agreed to submit a request for specific accounts under a 1996 tax treaty and a follow-up agreement in 2003. Under that accord, Swiss bank secrecy doesn't protect accounts if the owner engaged in "tax fraud or the like," which is a narrower definition of tax evasion than U.S. law provides.

The Swiss directed UBS to turn over accounts to the Swiss Federal Tax Administration for review before handing them to the IRS. Negotiators are determining how to apply the 1996 tax treaty and one adopted in 2009 that still needs ratification by the U.S. Senate, the people said.

"Switzerland is continuing talks with the U.S. authorities on administrative assistance in cases of tax fraud and tax evasion," said Norbert Baerlocher, spokesman for the Swiss embassy in Washington, in a statement. "Any exchange of client data can occur only within the scope of the current legal system, in accordance with the procedures provided for in the existing or the new double-taxation agreement with the USA."

The Swiss agreed in March 2009 to meet international standards to avoid being blacklisted as a tax haven by the Organization for Economic Cooperation and Development. The London-based Tax Justice Network this month ranked Switzerland at the top of its financial secrecy index.

"This is a big issue for these banks," said C. Evan Stewart, an attorney at Zuckerman Spaeder LLP in New York, who isn't involved in the settlement talks.

"These are no longer small institutions catering to wealthy people in a small part of central Europe," he said. "These are multinational institutions now that have a reach that's all over the world. This has a huge impact on the banking system in Switzerland. Another issue is the sovereignty in Switzerland and whether that will be given deference by other governments."

The IRS has said 30,000 U.S. taxpayers with offshore accounts avoided prosecution since 2009 by entering a limited amnesty program, paying back taxes and saying who helped them hide their accounts from authorities. Hundreds of taxpayers in the program have given information to prosecutors that have helped them build criminal cases against bankers and advisers.

"The DOJ and IRS are casting a wide net as they try to identify Americans guilty of offshore tax evasion," said Aaron D. Schumacher, a Geneva-based wealth planning attorney, with Withers LLP.