LONDON (Reuters) - Britain has appointed a senior judge to hold an inquest into the death of Alexander Litvinenko, the former Russian agent turned Kremlin critic whose death from polonium poisoning in London in 2006 soured relations between London and Moscow.
Litvinenko, who had been granted British citizenship, was poisoned with polonium-210, a rare and highly toxic radioactive isotope, which was slipped to him in a cup of tea at a plush London hotel.
Britain's Judicial Office said on Thursday it had selected Robert Owen, an experienced judge, for the task and that he would hold a hearing in September to decide how the inquest would be conducted and whether it would be heard before a jury.
Litvinenko's widow Marina, who lives in Britain, has long argued that the Russian state was complicit in her husband's murder and demanded a wide-ranging inquest into his death.
She welcomed the inquiry: "I am just happy."
Britain rarely appoints judges to take charge of an inquest, reserving them for the most complex and high-profile cases, such as the 1997 death of Princess Diana in Paris or the killings of London commuters in suicide bomb attacks in 2005.
The announcement could complicate Britain's efforts to improve relations with Russia - London has been keen to prevent the Litvenenko case from derailing trade ties with Russia.
It also comes just a week after Russian President Vladimir Putin made his first visit to London in nine years to watch judo at the Olympics with British Prime Minister David Cameron. The two men did not discuss the case in those talks, say officials.
The Judicial Office, which is independent of government ministers, said the timing of the inquest announcement was unconnected to Putin's visit or political considerations.
Relations between Britain and Russia plunged to a post-Cold War low after Litvinenko's killing complete with tit-for-tat diplomatic expulsions.
Russia has since refused to extradite Andrei Lugovoy, the ex-KGB bodyguard Britain wants to prosecute for Litvinenko's murder by poisoning with radioactive polonium.
Lugovoy, who was later elected to Russia's lower house of parliament, has denied any involvement.
Alexander Goldfarb, a close friend of Litvinenko, said he hoped the inquest would hear evidence from British secret services and be shown undisclosed details of the British police inquiry into the death.
Scotland Yard had no immediate comment but has previously said it would hand over any information sought by a coroner. An earlier hearing called on the security services to conduct further inquiries.
"This inquest will hopefully give some closure to Marina and also it will show the truth," said Goldfarb, who co-wrote a book with Litvinenko's wife about her husband's death.
"And the truth as we know is this was a state-sponsored terrorist attack and that the Russian government and Mr Putin are involved," he added.
The Kremlin rejects such allegations and denies any involvement by Putin or the Russian government in Litvinenko's death.
Russian authorities say the British focus on Lugovoy as the suspect is the result of anti-Russian bias and say Britain has failed to provide evidence of his guilt.
Moscow has used the case, and its refusal to extradite Lugovoy, to show Russians that the government stands up to the West and protects its own.
Russia is particularly sensitive about the affair because Litvinenko was an associate of tycoon Boris Berezovsky, a former Kremlin insider who became a fierce critic of President Vladimir Putin and was granted asylum in Britain.
Berezovsky said the Kremlin had a hand in the poisoning, while the Kremlin accused him of exploiting the Litvinenko case to discredit Putin.
Britain's Foreign Office said the inquest was a judicial matter but that the government remained committed to seeking justice over the death.
"This was a crime which took place in the UK and involved a British citizen. Our aim remains to see this matter tried in a UK court," a Foreign Office spokesman said.
Litvinenko's lawyer Louise Christian welcomed the appointment of Owen to preside over the inquest.
"The inquest cannot impute civil or criminal liability but it can deliver a full and fearless inquiry into what happened," she said. "Marina wants the inquest to uncover the truth about her husband's death - who murdered him and why."
(Additional reporting by Steve Guttman in Moscow)