Russia's top prosecutor has dismissed a lawmaker's suggestion that the country engage in an extradition swap with Britain.

The lawmaker had proposed extraditing former intelligence agent Andrei Lugovoi, a suspect in the poisoning of a former Russian intelligence agent, in exchange for Boris Berezovsky, a business tycoon wanted by Moscow who has been living in exile in Britain.

Officials at the office of Russia's prosecutor general say they are not even considering the idea, as the country's constitution prohibits extraditing citizens. British authorities have also rejected the proposed exchange.

London has requested the extradition of Lugovoi to stand trial in Britain for the murder of Alexander Litvinenko, who died late last year after being poisoned with polonium-210.

Russia has been seeking the extradition of Berezovsky, wanted on corruption charges, which the tycoon has called political. Britain has rejected the Russian requests.

A White House spokesman, Gordon Johndroe, said Wednesday the United States backs Britain's request for Lugovoi's extradition from Russia, calling the Litvinenko killing a serious crime that needs to be dealt with.

British police determined that Litvinenko met with Lugovoi and another Russian businessman at a London hotel November first, the day Litvinenko fell ill.

In a letter on his deathbed, Litvinenko accused Russian President Vladimir Putin of having ordered his poisoning. The Kremlin denies any involvement.

Some information for this report provided by AFP and Reuters.