A United States judge says the country's attorney general must respond to Switzerland's complaints over a legal case between UBS and the Internal Revenue Service.

The IRS has taken Switzerland's largest bank to court in a bid to force it to disclose the identities of about 52,000 Americans it suspects of using Swiss accounts to hide $14.8 billion (SFr16.7 million) in assets and avoid paying US taxes.

The Swiss government one week ago asked Alan Gold, a US district judge, to block the proceedings because forcing UBS to hand over client data would violate Swiss sovereignty and break international laws.

Gold said in Miami on Thursday that the Swiss have a point.

"In our view, the issues raised by the government of Switzerland warrant an expression of interest...that directly addresses the issues," he ruled. "I am requesting the United States attorney general to directly respond."

The Swiss government, which has not been named in the UBS case, has said the legal battle with the American tax authority could derail talks underway with Washington on accords designed to ease Switzerland's long-standing banking-secrecy laws.

UBS admitted in February it helped US clients hide assets from the IRS. The bank agreed to pay $780 million in fines and has since revealed the names of 320 American clients.

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