ZURICH (AP) — Swiss bank UBS AG, which is being investigated by the US for tax fraud, said yesterday that it has forbidden its travel client managers from travelling abroad.

UBS managers who handle clients from countries other than Switzerland are barred from going overseas, spokeswoman Eveline Mueller said.

Mueller declined to say whether the restriction aimed at protecting UBS managers from US authorities. The travel ban affected the bank's international business with all countries, she said.

UBS has been involved in a dispute with the US over wealthy Americans who have assets in Switzerland's biggest bank. It is assessing the guidelines and rules of behaviour related to its international asset management business, Mueller said.

The bank has provided US tax authorities with the details of 255 wealthy Americans suspected of tax fraud, but refuses to identify about 50,000 more US account holders Washington wants. Former UBS manager Martin Liechti was held over two months for witness questioning in the US last year in connection with the tax fraud investigation.