The US embassy in Moscow is reportedly keen to resolve the issue

The 20-year lease was set in 1985. But the rouble's value has since plunged by more than 99.9%, slashing the mansion's annual rent, Interfax news agency said.

Spaso House is one of the smartest residences in Moscow, where rents have soared to rival western capitals.

Russia has complained several times before about rent for the mansion.

In 2001, the foreign ministry office in charge of the matter threatened to take the issue to international arbitration.

Literary landmark

The US should pay some $9m to the government to make up for the bargain it has been getting, the office head was quoted as saying by Interfax on Monday.

A US embassy spokesman said the US was keen to resolve the issue, AP news agency reported.

But he noted that Soviet officials insisted that no provisions be made for currency fluctuations when the lease was negotiated.

Spaso House was built in 1914 for a rich merchant and was seized by communist revolutionaries, before becoming home to the US envoy in 1930s.

The mansion is also a literary landmark. It is the site of a 1935 ball that author Mikhail Bulgakov reportedly used as the model for the masked ball in his novel, The Master and Margarita.