(Reuters) – The Swiss government is considering a possible solution to a long-running dispute with U.S. authorities over Swiss banks accused of helping wealthy Americans evade billions of dollars of tax.

A source familiar with the talks has told Reuters the two sides have agreed an outline for a deal that would divide over 300 Swiss banks according to the extent they had helped U.S. clients hide money, to determine how they are dealt with.

A Swiss government spokesman said in a statement on Wednesday the cabinet had been informed about a solution to the dispute. He declined to give further details as the negotiations are ongoing.

Bank secrecy, which has helped Switzerland become the world’s largest offshore center with $2 trillion in assets, has come under heavy fire since the financial crisis as cash-strapped governments have sought to clamp down on tax evasion.

The Swiss government has been in protracted talks to end U.S. investigations into Swiss banks, including Credit Suisse (CSGN.VX) and Julius Baer (BAER.VX), in return for expected heavy fines and a transfer of client names.

Under the outline deal, banks already under investigation would settle with individual deferred prosecution agreements, the source said.

Credit Suisse, which has already made a 295 million Swiss franc ($318.35 million) provision towards settling the investigation, declined to comment. The Swiss Bankers Association also declined to comment.

A second group of banks which had U.S. clients but have not yet been targeted by investigators would have to agree to pay fines and hand over data on their customers, the source said.

The country’s biggest bank UBS (UBSN.VX) was forced in 2009 to pay a fine of $780 million and hand over the names of more than 4,000 clients, delivering the U.S. authorities information that allowed them to then pursue other Swiss banks.

Switzerland’s oldest private bank, Wegelin & Co, said in January it was closing down after pleading guilty to helping Americans evade taxes, paying a fine of nearly $58 million.

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