United States officials have given Switzerland an ultimatum to hand over details on the number of Americans who used Swiss banks to cheat on their taxes, according to Swiss media reports.

Zurich weekly SonntagsZeitung says US Deputy Attorney General James Cole set the deadline in a letter sent to senior Swiss diplomat Michael Ambuehl last Wednesday.

The newspaper says it has seen a copy of the letter in which Cole demands to know how many Americans avoided paying taxes by hiding money in Swiss banks.

The NZZ am Sonntag newspaper cites unnamed Swiss officials as saying the US is threatening to charge one or more Swiss banks unless the information is received.