According to the Swiss daily TagesAnzeiger, Swiss authorities, in a confidential letter to 10 local banks said the US request could "be partially agreed upon", but that the data transfer would have to be done by the banks themselves, and not the government.
Furthermore, the letter said the banks would need to provide data on banking activities only going back to September 30th 2009. Prior to that date, information should only be provided "if there is a violation of US legislation or obvious tax fraud", the newspaper said.
On Wednesday, Switzerland's President Micheline Calmy-Rey told reporters that Swiss authorities had not provided the names of any clients of Swiss banks to US tax authorities.
"For Switzerland, any exchange of information on client data is only possible if it is based on existing legislation," she said, referring to the double taxation treaty reached in 2009 with the United States.
Last week, local weekly SonntagsZeitung reported that Washington had asked for detailed information on US nationals who might have improperly hidden money in Switzerland, basing its report on a purported letter from the US deputy attorney general James Cole dated August 31st, addressed to Swiss authorities.
US authorities want all data concerning private customers and US foundations which have deposited at least $50,000 (€35,300) in Switzerland between 2002 and July 2010, it said.