The former Russian nuclear minister, Yevgeny Adamov, detained in Switzerland for the past four months, has agreed to be extradited to Russia.
Accused by the United States of stealing money intended to improve Russia's nuclear security, Adamov wants to be judged for his alleged crimes in his homeland.
"He has declared himself willing to be prosecuted by Russian officials for the crimes that the United States accuses him of," said Folco Galli, spokesman for the Federal Justice Office.
Galli added that based on Adamov's request, the justice office decided last week to approve the extradition to Russia and asked US officials whether they would accept that decision.
The Americans have yet to give their answer, said the spokesman. Adamov will remain in Swiss detention pending a final decision on the competing US extradition bid.
Adamov has been held in Switzerland since he was arrested on May 2 on an American request while visiting his daughter in Bern.
He has since been indicted by a federal grand jury in Pittsburgh, Pennsylvania, on charges of conspiracy to transfer stolen money and securities, conspiracy to defraud the US, money laundering and tax evasion.
Russian authorities, concerned that he could divulge nuclear secrets if extradited to the US, have demanded he be sent to Russia to face charges there.
If the dispute between the United States and Russia continues, Switzerland will have to decide where to extradite Adamov based on the seriousness and location of the alleged crimes, the dates of the extradition requests and the nationality of the person involved.
The former minister's case has already been heard by the Federal Criminal Court in Bellinzona, which ruled that he must stay behind bars pending a decision on his extradition.
The US accuses him of stealing at least $9 million (SFr11.3 million) between 1993 and 2003 earmarked for improving Russia's nuclear security. Washington wants him extradited to face fraud charges.
In its own extradition demand, filed later, Moscow accused Adamov of fraud between 1998 and 2001 during his term of office.
The ex-minister has not denied he put money into private accounts but has said this was normal practice in Russia to shield money from hyperinflation, an unstable banking system and corruption rife after the collapse of communism.
swissinfo with agencies
Yevgeny Adamov was Russia's atomic energy minister from 1998 to 2001, when a parliamentary commission accused him of corruption.
He is charged by the US with embezzling funds that had been destined for nuclear-safety upgrades in Russia.
Adamov also faces extradition to Russia, which handed a formal request to the Swiss authorities on May 17, on fraud charges.
On June 9, the Federal Criminal Court ordered his release, but this decision was overturned by the Federal Court in Lausanne ten days later.