Andrei Nekrasov, who was friends with Litvinenko, said "Rebellion: The Litvinenko Case" would be shown at Cannes Saturday, with Litvinenko's widow, Marina, expected to speak at a preview press conference.
French television channel TV5 said the film was a last-minute addition to the festival's program by Cannes Artistic Director Thierry Fremaux, who compared the movie to a "big bang."
On Tuesday, British investigators completed their inquiry into the murder of Litvinenko, who died in London last November after being poisoned with the radioactive element polonium-210.
British prosecutors charged businessman Andrei Lugovoi, a former FSB bodyguard, with poisoning Litvinenko, and asked Russian authorities for his extradition - a request flatly rejected by Russia's Prosecutor General's Office, which said the suspect, a Russian national, could only be tried in his home country.
Lugovoi denied any involvement in Litvinenko's murder, dismissing the charges as politically motivated.
After Britain's Crown Prosecution Service said it would demand Lugovoi's extradition, Marina Litvinenko issued a statement saying she was looking forward to seeing him extradited and brought to trial in the U.K.
But she added in a later interview with British television that Lugovoi could not possibly be the only one responsible for her husband's murder.
"We don't know why my husband was killed, and who asked for this murder. I believe it was not only one person," she said.
A member of Russia's ultranationalist LDPR party, Alexei Mitrofanov, has suggested that Lugovoi should go to the U.K. and try to prove his innocence to British prosecutors without hiding behind the Russian government's back. That would make the situation with the extradition request less embarrassing to Russian authorities, he said.
"I would ask Lugovoi personally to go to England without creating further problems," Mitrofanov said. "If he is so sure of his innocence, he will be able to prove it with the help of defense lawyers."