U.S. authorities are ratcheting up pressure on Credit Suisse to plead guilty to helping wealthy Americans hide untaxed money in Swiss bank accounts, Swiss newspaper NZZ am Sonntag said.

The source quoted by the newspaper said U.S. authorities had made "extreme" demands regarding potential fines and wanted the names of all U.S. citizens who had stashed away untaxed money in Credit Suisse accounts, NZZ am Sonntag said.