A former Russian nuclear energy minister is to oppose a move by Moscow to have him extradited from Switzerland on corruption charges.
Mr Adamov wants to go to Russia as a free man
Yevgeny Adamov was held on a US warrant accusing him of misappropriating funds allotted by Washington for security in Russian nuclear facilities.
Mr Adamov's legal team said he wanted to return to Russia to fight the charges, but as a free man.
The US authorities are also seeking Mr Adamov's extradition.
They have until 30 June to make a request.
The BBC's Steve Rosenberg in Moscow says Mr Adamov has triggered a judicial tug-of-war between east and west.
The possibility of such a senior figure being extradited to the US had set alarm bells ringing in Russia, he says.
Mr Adamov was arrested on 2 May on a warrant issued in the US city of Pittsburgh, Pennsylvania, on suspicion that he embezzled $9m.
But the Russian justice ministry announced last week that a criminal case had been opened against him in Moscow.
The former minister said he would fight attempts to remove him by force.
"I wish to hereby inform you, that I am rejecting a simplified extradition to both requesting parties," Mr Adamov said in a statement read out by lawyers.
"The incarceration of my person, demanded by the United States of America, is illegal. I intend to leave prison as a free man and to return to my homeland as a free man."
Mr Adamov was nuclear energy minister from 1998 to 2001.
Russian politicians have warned that he possessed detailed knowledge of Russia's nuclear weapons programme - secrets which could not be allowed to fall into US hands.
One ultra-nationalist MP even called for Mr Adamov to be assassinated to make sure no secrets leaked out.