Sunday newspaper Der Sonntag quoted from an unpublished additional report to the revised double taxation agreement with the United States that would allow US authorities to obtain client data without clearly identifying suspected tax dodgers.

In the report, Switzerland assures the United States it will not only treat requests for administrative assistance based on names or other personal data but also those relying on behavioural patterns.

"In these requests, people are not identified directly via a name or an insurance number but via a behavioural pattern," the government wrote in the report published by the newspaper which will be submitted to the Swiss parliament this autumn.

Switzerland's tradition of bank secrecy, which has been used by tax evaders to hide money in secret accounts, has come under pressure in recent years as cash-stripped governments try to crack down on tax dodgers.

US authorities have forced the Alpine country to bend its own bank secrecy law by handing over data on some 4,450 clients of its largest bank UBS and now also has the country's second-largest bank Credit Suisse, as well as several smaller institutions, on its radar screen.

Switzerland has so far rejected the idea of anonymous mass requests for client data, or so-called "fishing expeditions", but may now have to make further concessions as the noose is tightening on Credit Suisse, Der Sonntag said.

Switzerland's finance minister Eveline Widmer-Schlumpf said earlier this week Switzerland had made a proposal to try to kickstart talks to settle its impasse with US authorities.

Earlier this month, Switzerland struck deals with Germany and Britain to tax money kept by the two countries' residents in secret Swiss accounts.