Main suspect in Litvinenko poisoning ready to help investigation
Lugovoy is wanted by the British authorities, but remains in Russia where the constitution prohibits his extradition.
He wants guarantees from the British government and an assurance that Kovtun will not be extradited to Germany, where he is under investigation.
Both vehemently deny any involvement in the murder.
Sunday marks two years since Aleksandr Litvinenko died in agony in a London hospital from radioactive poisoning.
Diplomatic war rages between Russia, UK