A major London exhibition of French and Russian paintings could be cancelled by Russian authorities over fears the art could be seized while on British soil.
The Hermitage had planned to loan Pablo Picasso's Dryad
From Russia: French and Russian Master Paintings is due to open at the Royal Academy of Arts in January.
But the exhibition is at risk if authorities in Russia do not issue export licences for works that include paintings by Picasso and Van Gogh.
The Russian Ministry of Culture said a decision would be made on Thursday.
The Royal Academy said it had not received any official notification regarding the exhibition and was "seeking clarification".
It had earlier assured Russia that the works were protected under British law and could not be seized to settle private legal claims.
The exhibition, which includes works from the State Hermitage Museum in St Petersburg and Moscow's Pushkin Fine Arts Museum, is currently in Dusseldorf, Germany.
Some of the art was taken from private collections after the 1917 revolution, leading to fears of seizure.
Gordon Brown and Vladimir Putin are scheduled to attend the show's opening.
Former shadow arts minister Hugo Swire, who used to work for the National Gallery, told the BBC it was difficult to see what was behind the situation.
The Conservative MP, who organised an exhibition of Russian art in London during the Gorbachev era, said issues such as the Litvinenko row or the closure of British Council offices in Russia could be to blame.
"I think this is a situation that certainly the Royal Academy were nervous might happen," he said.
"I had a discussion with the then director about this very situation, and the government I don't think have been very quick to come forward to address the potential of something like this happening."