Bowing to international pressure, Switzerland announced on Friday that it would move toward a more rigid definition of tax evasion and help global authorities pursue tax cheats.

The surprise announcement came after a similar shift by two other European tax havens, Liechtenstein and Andorra, on Thursday.

Together the moves deal the biggest blow yet to European traditions of banking secrecy and come amid a global crackdown on tax evasion. The three governments agreed to cooperate with authorities in the United States and elsewhere in investigating tax evasion and, under certain circumstances, to turn over data on accounts at banks headquartered within their jurisdictions.

"The adoption of the O.E.C.D standards is a significant signal that bank secrecy as it has existed for generations is coming to an end," said Scott D. Michel, a tax lawyer at Caplin & Drysdale in Washington, D.C.