Switzerland and the United States need more time to negotiate a tax deal, Swiss finance minister Eveline Widmer-Schlumpf told Swiss radio on Saturday, as the United States pushes for it to supply information on bank clients who are alleged to have evaded taxes.

We have made a lot of progress with the main point of the treaty, but we are not there yet where we want to be from a Swiss point of view. The demands of the Americans and the expectations of the Swiss are not yet in line and it will certainly need more talks, Widmer-Schlumpf said.

Eleven Swiss banks, including Credit Suisse , Julius Baer and Basler Kantonalbank , are under formal investigation by the U.S. tax authorities.

Widmer-Schlumpf declined to give details on possible fines facing the banks involved.

Last month, Widmer-Schlumpf, who will take up the rotating role of president in 2012, said she expected an agreement before the year's end with the United States on measures to deliver bank details of suspected U.S. tax evaders.

Switzerland reached a deal with U.S. officials in 2009 for UBS to reveal details of around 4,450 clients, averting criminal charges.

(Reporting by Katie Reid)