FILE - In this file photo taken on Thursday, March 30, 2017, Russian opposition leader Alexei Navalny, right, shows a V-sign for the media in court in Moscow, Russia. Russian opposition politician Alexei Navalny is in a coma and on a ventilator in an intensive care unit in Siberia after falling ill from suspected poisoning that his allies believe is linked to his political activity. (AP Photo/Evgeny Feldman, File)

FILE - In this file photo taken on Wednesday, July 10, 2013, police officers detain Russian opposition leader Alexei Navalny, center, in Moscow, Russia. Russian opposition politician Alexei Navalny is in a coma and on a ventilator in an intensive care unit in Siberia after falling ill from suspected poisoning that his allies believe is linked to his political activity. (AP Photo/Evgeny Feldman, File)

Russian opposition activist Alexei Navalny's wife Yulia leaves a hospital intensive care unit where Alexei Navalny is hospitalized in Omsk, Russia, Thursday, Aug. 20, 2020. Russian opposition politician Alexei Navalny is on a hospital ventilator in a coma, after falling ill from a suspected poisoning, according to his spokeswoman Kira Yarmysh. (AP Photo/Stepan Izvekov)

FILE - In this Saturday, July 20, 2019 file photo Russian opposition activist Alexei Navalny gestures while speaking to a crowd during a political protest in Moscow, Russia. Russian opposition politician Alexei Navalny was placed on a ventilator in a hospital intensive care unit in Siberia after falling ill from suspected poisoning during a flight, his spokeswoman said Thursday Aug. 20, 2020. (AP Photo/Pavel Golovkin, File)

FILE - In this Wednesday, Sept. 5, 2018 file photo Russian opposition leader Alexei Navalny stands during a break in the hearing on his appeal in a court in Moscow, Russia. Russian opposition politician Alexei Navalny was placed on a ventilator in a hospital intensive care unit in Siberia after falling ill from suspected poisoning during a flight, his spokeswoman said Thursday Aug. 20, 2020. (AP Photo/Pavel Golovkin, File)

In this handout photo taken provided gluchinskiy, Russian opposition leader Alexei Navalny, center, and Kira Yarmysh, foreground left, pose for a selfie inside a bus on their way to an aircraft at an airport outside Tomsk, a city in Siberia, Russia Thursday, Aug. 20, 2020. Russian opposition leader Alexei Navalny is in a coma in a hospital in Siberia after falling ill from a suspected poisoning. His spokeswoman said Navalny felt unwell on a flight to Moscow and the plane made an emergency landing. (gluchinskiy via AP)

Police officers detain a protester as he comes to support Russian opposition leader Alexei Navalny in front of the building of the Federal Security Service (FSB, Soviet KGB successor) in Moscow, Russia, Thursday, Aug. 20, 2020. The banner reads: "Navalny live!!! Politkovskaya? Nemtsov? Who is next? Putin is a thief" Russian opposition politician Alexei Navalny is on a hospital ventilator in a coma, after falling ill from a suspected poisoning, according to his spokeswoman Kira Yarmysh. (AP Photo/Pavel Golovkin)

An ambulance is parked outside the hospital intensive care unit where Alexei Navalny is hospitalized in Omsk, Russia, Thursday, Aug. 20, 2020. Russian opposition politician Alexei Navalny is on a hospital ventilator in a coma, after falling ill from a suspected poisoning, according to his spokeswoman Kira Yarmysh. (AP Photo/Evgeniy Sofiychuk)

Anatoliy Kalinichenko, deputy chief doctor of the Omsk hospital of intensive care where Alexei Navalny is hospitalized speaks to the media in Omsk, Russia, Thursday, Aug. 20, 2020. Russian opposition politician Alexei Navalny is on a hospital ventilator in a coma, after falling ill from a suspected poisoning, according to his spokeswoman Kira Yarmysh. (AP Photo/Evgeniy Sofiychuk)

Ambulances are parked outside the hospital intensive care unit where Alexei Navalny is hospitalized in Omsk, Russia, Thursday, Aug. 20, 2020. Russian opposition politician Alexei Navalny is on a hospital ventilator in a coma, after falling ill from a suspected poisoning, according to his spokeswoman Kira Yarmysh. (AP Photo/Evgeniy Sofiychuk)

FILE - In this Sunday, Feb. 24, 2019 file photo, Russian opposition activist Alexei Navalny takes part in a march in memory of opposition leader Boris Nemtsov in Moscow, Russia. Russian opposition politician Alexei Navalny was placed on a ventilator in a hospital intensive care unit in Siberia after falling ill from suspected poisoning during a flight, his spokeswoman said Thursday Aug. 20, 2020. (AP Photo/Pavel Golovkin, File)

Russian President Vladimir Putin attends a meeting via video conference at the Novo-Ogaryovo residence outside Moscow, Russia, Thursday, Aug. 20, 2020. (Alexei Nikolsky, Sputnik, Kremlin Pool Photo via AP)

A protester stands in front of a police officer holding a poster reading "Putin stop poisoning people!" during a picket in support of Russian opposition leader Alexei Navalny in the center of St. Petersburg, Russia, Thursday, Aug. 20, 2020. Russian opposition politician Alexei Navalny is on a hospital ventilator in a coma, after falling ill from a suspected poisoning, according to his spokeswoman Kira Yarmysh. (AP Photo/Elena Ignatyeva)

A protester stands holds a poster reads "poison is the weapon of a woman, a coward and a eunuch!" during a picket in support of Russian opposition leader Alexei Navalny in the center of St. Petersburg, Russia, Thursday, Aug. 20, 2020. Russian opposition politician Alexei Navalny is on a hospital ventilator in a coma, after falling ill from a suspected poisoning, according to his spokeswoman Kira Yarmysh. (AP Photo/Elena Ignatyeva)

FILE - In this Monday, Aug. 27, 2018 file photo, Russian opposition leader Alexei Navalny gestures while speaking in a court room in Moscow, Russia. Russian opposition politician Alexei Navalny was placed on a ventilator in a hospital intensive care unit in Siberia after falling ill from suspected poisoning during a flight, his spokeswoman said Thursday Aug. 20, 2020. (AP Photo/Pavel Golovkin, File)

FILE - In this file photo taken on Thursday, April 27, 2017, Yulia, wife of Russian opposition leader Alexei Navalny treats him after unknown attackers doused him with green antiseptic outside a conference venue in Moscow, Russia. Russian opposition politician Alexei Navalny is in a coma and on a ventilator in an intensive care unit in Siberia after falling ill from suspected poisoning that his allies believe is linked to his political activity. (AP Photo/Evgeny Feldman)

FILE - In this file photo taken on Monday, Dec. 25, 2017, Russian opposition leader Alexei Navalny, who submitted endorsement papers necessary for his registration as a presidential candidate, center, heads to attend a meeting in the Russia's Central Election commission in Moscow, Russia. Russian opposition politician Alexei Navalny is in a coma and on a ventilator in an intensive care unit in Siberia after falling ill from suspected poisoning that his allies believe is linked to his political activity. (AP Photo/Evgeny Feldman)