Litvinenko, an outspoken Kremlin critic with ties to exiled Russian oligarch Boris Berezovsky, defected in 2000 and received a British passport shortly before he died in a London hospital at the age of 43. Doctors said traces of radioactive polonium-210 were found in his body.
"We have established very good and constructive relations with British experts and signed a cooperation agreement with them," Yuri Chaika said in a televised interview with the Vesti Nedeli program on Rossiya television channel.
Detectives from Scotland Yard and the Russian Prosecutor General's Office have been investigating the case in London and Moscow, where key witnesses, agents-turned-businessmen Andrei Lugovoi and Dmitry Kovtun, are based.
The two men met with Litvinenko in a London hotel shortly before he was hospitalized with symptoms of poisoning, and have themselves undergone radiation checks. Both have denied any involvement in Litvinenko's death.
Police in Germany found traces of polonium-210 in several locations in Hamburg where Kovtun's former wife and mother-in-law live.
Chaika said Russian investigators are preparing for a trip to Britain to inspect some venues, the place of poisoning and attend questionings to be held by their British colleagues.
