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. Last Updated: 07/27/2016

Quid Pro Quo in Litvinenko Probe

British detectives probing the death of former security services agent Alexander Litvinenko want to return to Russia for a second round of interviews.

Prosecutor General Yury Chaika said Tuesday that authorities in Moscow had received a request Monday from the London Metropolitan Police for permission to send the detectives.

The request appears to set up a quid pro quo between London and Moscow: The British are said to want more information from Andrei Lugovoi, Dmitry Kovtun and Vyacheslav Sokolenko, all of whom are considered possible suspects. The Russians want to speak with Russian tycoon Boris Berezovsky and Chechen rebel envoy Akhmed Zakayev.

As Alex Goldfarb, a Litvinenko friend and Kremlin critic, put it, the current situation looks like a "thinly veiled condition. If the Russians get access to Berezovsky and Zakayev, then it would be harder for the Russians to turn down British requests to speak again with Lugovoi and Kovtun in Moscow."

Neither Berezovsky nor Zakayev could be reached for comment Tuesday. Goldfarb said he had spoken with Berezovsky on Monday and that Berezovsky would cooperate with the investigation. "If the British authorities request an interview from Berezovsky, he will cooperate," Goldfarb said. "But that's only if the British ask."

Goldfarb, a Soviet-era refusenik, added: "This whole thing is a farce," he said. "The Russians have no business in London."

Goldfarb also said he would only agree to speak with Russian authorities in London "if British security experts can rule out the possibility of the Russians putting polonium in my tea."

Litvinenko died Nov. 23, a little more than three weeks after ingesting the radioactive isotope polonium-210.

In a deathbed statement, Litvinenko, a former KGB and Federal Security Service agent, blamed President Vladimir Putin for his poisoning. The Kremlin has denied any involvement.

Litvinenko fell ill after meeting on Nov. 1 with Lugovoi, also a former security services agent; Kovtun, a businessman; and Sokolenko, head of a private Russian security firm. The four met at a bar at the Millennium Hotel in London.

All three men have denied having anything do with Litvinenko's death.

On their first trip to Moscow, from Dec. 4 to Dec. 20, British detectives were permitted to watch Russian investigators interview Lugovoi and Kovtun. It is unknown whether Sokolenko was questioned at the time.

Lugovoi, reached by telephone Tuesday, said he had no new information to give British authorities. During a December interview with Russian detectives -- from a hospital bed at a Moscow clinic where he was undergoing tests for radiation poisoning -- Lugovoi said he would be willing to meet with British detectives again.

Sokolenko declined to comment on the Litvinenko investigation in a brief telephone conversation Tuesday, saying only that he was "fed up" with the case. "I have nothing to do with the poisoning whatsoever," he said, before hanging up.

German authorities found traces of polonium-210 in several locations in Hamburg, which Kovtun visited before continuing on to London for his meeting with Litvinenko. Kovtun could not be reached for comment Tuesday.

Crime experts say repeat interrogations are essential to a complete investigation.

Mark Galeotti, director of Keele University's Organized Russian and Eurasian Crime Research Unit, in England, said detectives would have no choice but to interview Lugovoi and Kovtun again if they unearthed new information.

Despite possible concerns that Moscow will deny British detectives access, Dmitry Peskov, a spokesman for the presidential administration, said Scotland Yard investigators would "most likely be free to speak to Lugovoi and Kovtun again."

A source at the Prosecutor General's Office, who spoke on the condition of anonymity, backed up Peskov, indicating that officials in Moscow were open to giving the British access to suspects in the Litvinenko case.

Chaika, for his part, suggested that British detectives would be welcomed back to Russia only after Russian authorities had visited London.

"It's very likely that once our representatives have visited London, we will welcome our [British] colleagues here," Chaika said, Interfax reported.

Russian authorities have strongly hinted that Berezovsky, who in 2000 fled the country after a falling out with Putin, is a suspect in the Litvinenko case. British detectives have interviewed Berezovsky but are not believed to consider him a suspect.

"We don't rule out that murder was carried out by a Russian living abroad," Chaika said. Referring to Berezovsky, who is wanted in Russia on multiple charges, including plotting a violent coup, Chaika added: "We intend to question him only about the Litvinenko case."

Zakayev, a Chechen rebel envoy, was a neighbor and close friend of Litvinenko. He is also an outspoken critic of Putin.

State-controlled media in Russia have speculated that Berezovsky had Litvinenko killed in an attempt to discredit the Kremlin.