Swiss news reports say the United States has presented an ultimatum to Switzerland, demanding that it provide detailed information about thousands more U.S. citizens suspected of using Swiss banks to cheat on their taxes.

The reports quote an August 31 letter from U.S. Deputy Attorney General James Cole requesting detailed data on suspected tax evasion at Credit Suisse (UBS) and as many as nine other smaller Swiss banks. The reports say failure to comply by Tuesday could mean criminal charges against one or more of the banks.

Neither the Swiss nor U.S. governments has commented on the reports, which appeared Sunday in the newspapers (SonntagsZeitung and the NXX am Sonntag).

One of the reports (SonntagsZeitung) quotes officials close to the case as saying Washington wants details on the number of Americans with accounts containing more than $50,000 with UBS and at least four other banks between 2002 and 2010.

Last year, under intensifying U.S. pressure, the Swiss parliament gave final approval to a deal permitting Credit Suisse to provide the names of nearly 4,500 U.S. clients suspected of hiding hundreds of millions of dollars to avoid paying U.S. taxes. U.S. officials later said many of the UBS clients under scrutiny simply shifted their assets to smaller Swiss banks to avoid declaring them.

The Swiss government has since signed deals with Germany and Britain to provide greater assistance to foreign tax authorities.