"We want to organize the best Games possible," IOC President Thomas Bach said, adding that "this postponement will require sacrifices and compromises from all parties."
International Olympic Committee member Dick Pound says the details have not been finalized, amid increasing calls for the 2020 Summer Games to be postponed.
French prosecutors suspect the Tokyo bid committee of paying bribes to host the 2020 Games. Tsunekazu Takeda, who also chairs the IOC's Marketing Commission, maintains his innocence.
An art as much as it is a sport, parkour's urban ethic is one of bold, practiced risk-taking. Now its adherents say it is having to fight against encroachment by powerful interests.
"Without any doubt, we will not declare any blockade, we will not prevent our Olympians from taking part," Russian President Vladimir Putin said one day after the IOC's decision.
The decision by the International Olympic Committee follows last year's McLaren report, which said more than 1,000 Russian athletes were involved in manipulating doping controls.
The decision to award the 2024 and 2028 games simultaneously is a first for the International Olympic Committee and the result of a trying bidding process.
Paris and Los Angeles are the only remaining contestants for 2024 after four other cities dropped out. The committee's decision means the 2024 loser can avoid mounting an arduous new bid for 2028.
After the retesting of samples from the 2008 Beijing Olympics, dozens of athletes from six sports could be banned from the 2016 Games in Rio, the International Olympic Committee said.
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