WASHINGTON – The U.S. government and Switzerland have reached an agreement that could expose Americans who have used Swiss banks to avoid paying taxes.

The agreement will allow Swiss banks to settle any potential U.S. charges if they disclose extensive information about their American clients, the value of their accounts and any help they received from tax professionals.

Those settlements would include penalties for Swiss banks that helped their U.S. customers avoid taxes, according to a senior Justice Department official. The total penalties could top $1 billion, the official said. The department could also use the information to prosecute Americans for tax evasion.

The official shared details about the agreement during a conference call with reporters Wednesday. But the official did not speak on the record because it won’t be formally announced for a few days.

The agreement could be a big step toward resolving a long-running dispute between the two countries. Swiss banks would be able to turn over customer data without violating that country’s bank secrecy laws. At the same time, those banks could pursue legal settlements with the U.S. Justice Department and avoid criminal prosecution. But to do so, the banks would have to disclose reams of information about U.S. clients, including those who may have moved money out of the banks after the U.S. began its crackdown in 2009.

The agreement “enhances the department’s ability to follow the money, both within Switzerland and globally,” the official said.