On Thursday, the French economy minister, Christine Lagarde, and the Swiss president, Hans-Rudolf Merz, signed a revised tax treaty, long sought by Paris, that updated the two countries’ 1966 agreement to conform with the latest international standards set by the 30 nations of the Organization for Economic Cooperation and Development.

Ms. Lagarde hailed the agreement as “the start of a new era in relations between the two governments” and said Swiss bank secrecy laws would “no longer be an obstacle to the communication of this information.”

The onset of the financial crisis was the trigger for France, along with the United States and Germany, to begin a determined push for international cooperation against tax avoiders. Switzerland is by far the largest tax haven, and it has attracted most of the opprobrium and pressure this year.

In Washington, the Internal Revenue Service agreed Aug. 19 to a deal with the Swiss bank UBS under which it will obtain the names of 4,450 holders of accounts that it suspects Americans are using to avoid U.S. taxes. The Swiss bank had already agreed to pay $780 million to settle civil and criminal charges in the case.

President Nicolas Sarkozy of France is also seeking to shore up his bona fides as a reformer as he prepares for the Group of 20 nations summit meeting in Pittsburgh Sept. 24-25. Last week, Mr. Sarkozy obtained the agreement of French banks to curb excessive bonus payments, saying, “France must lead and try to persuade the others.”