US Treasury Secretary Timothy Geithner and Swiss Ambassador Urs Ziswiler signed a set of rules updating the income tax treaty, which was announced in June.

The new agreement calls for "greater tax information exchange" between the two countries, according to officials.

"Tax evasion is not simply an American issue, it is a global issue requiring global coordination," said Geithner.

"Today’s agreement strengthens our longstanding and cooperative relationship with Switzerland and will help serve as an example for others around the world," he said.

"Global efforts to end offshore tax evasion have never been stronger; we look forward to working with other nations to act against tax evasion and protect public finances and our financial systems."

The signing came as US officials prepared to control holders of hidden offshore accounts, helped by an agreement with Swiss banking giant UBS.

The settlement challenging Switzerland’s bank secrecy tradition resulted in the disclosure of the identities of 4,450 people with UBS offshore accounts and was expected to allow more prosecution of tax evasion.

US authorities Monday extended by some three weeks a tax amnesty deadline for holders of undisclosed offshore bank accounts, citing large numbers of people facing "logistical" issues coming forward.

The Internal Revenue Service said the deadline, which had been set for Wednesday, was extended to 15 October, but indicated there would be no further postponements.

AFP / Expatica