MIAMI -- A legal tactic the US Internal Revenue Service has used in an attempt to learn the identities of UBS AG's private-bank clients will now be deployed against other offshore-banking operations, an IRS agent told a conference.

In a showdown with UBS, the US Justice Department last July used a "John Doe" summons to investigate alleged tax fraud by people whose identities aren't known because of Switzerland's bank-secrecy laws. It marked the first time that a foreign bank had been served with such a summons.