Litvinenko, a Kremlin critic, died from radioactive poisoning in London in late November.
British detectives traveled to Moscow in December as part of the probe into his killing and Scotland Yard today said there were no definitive plans for them to return to Russia.
Chaika said his office wants to question fugitive Russian tycoon Boris Berezovsky as part of Russia's own investigation into Litvinenko's death.
Berezovsky, a strong Kremlin critic, lives in Britain, where he was granted political asylum.
Chaika said that as part of the Litvinenko probe, prosecutors were also seeking to question Leonid Nevzlin, a former shareholder of the bankrupt Yukos oil company who fled to Israel.
(Interfax, AFP, AP)
Aleksandr Litvinenko: A Timeline
CLOAK AND DAGGER: A timeline of a murder case that unraveled after Andrei Litvinenko, a former Russian security officer and vocal Kremlin critic, dies on November 23, 2006, of poisoning by radioactive isotope polonium-210.
In a deathbed letter, Litvinenko blames Russian President Vladimir Putin for his death -- a claim Putin condemns.
Investigators center on two meetings in London that Litvinenko had described -- one in which he met with two Russians for tea in London, and another in which he met with a third Russian at a sushi bar.
Six months later, British prosecutors announce they have enough evidence to charge a Russian citizen -- one of the men who had met with Litvinenko for tea -- with the murder ...more...
MORE: Coverage in Russian from RFE/RL's Russian Service.