Former Russian nuclear energy minister Yevgeny Adamov is to be extradited from Switzerland to the United States, the Swiss justice ministry has announced.
Yevgeny Adamov has gone on hunger strike in protest
The US accuses Mr Adamov of embezzling up to $9m (£4.9m) it gave to improve security at Russian nuclear facilities.
Russia has been fighting the move for fear his detailed knowledge of the country's nuclear weapons programme could fall into US hands.
It said the decision to extradite Mr Adamov was politically motivated.
"The [Swiss] federal justice authorities has taken a decision that runs counter to judicial and objective circumstances," a statement from the Russian Foreign Ministry said.
The former minister has 30 days to appeal to the Swiss federal supreme court against the US extradition order.
Mr Adamov was arrested in Switzerland in May on a warrant issued in the US. Moscow filed its own extradition request shortly afterwards.
A US federal grand jury has indicted him on charges of conspiracy to transfer stolen money, conspiracy to defraud the US, money laundering and tax evasion.
The nuclear physicist, who was Russia's nuclear minister from 1998 to 2001, denies the charges and has said he would prefer to be extradited to his homeland.
Swiss Justice Ministry spokesman Rudolf Wyss said the US request had been given precedence because it meant Mr Adamov could still be extradited to Russia once he had served any sentence imposed in the US.
If he had been sent back to Russia first, it would not have been possible to re-extradite him to Washington later, he said.
Mr Adamov started a hunger strike on Monday to press for extradition to Russia or release, Mr Wyss added.