The International Olympic Committee moved close to an agreement that will allow Paris and Los Angeles to each host the Summer Games between now and 2028 and rule out any other cities from bidding.
The two cities were the only ones left in the race to stage the 2024 Games and an IOC session voted that it would seek a "tri-partite agreement" for one host in 2024 and the other in 2028.
The original plan had been to choose one for 2024 at the next session in Lima on Sept. 13, discard the other and start a whole new bidding process for 2028.
For the agreement to work, either one or both cities would have to be willing to accept the 2028 Games if they were not awarded 2024, the IOC said.
The mayors of both cities said they would work towards reaching an agreement while IOC president Thomas Bach said he believed a deal could be struck by August.
"We will start right away," Bach told a news conference. "There are procedures to be followed in the two cities but I hope in August we could be there if everything goes well."
Bach said the decision would "ensure the stability of the Olympic Games for 11 years (which) is really, in our world, something extraordinary." He described it as a "win-win-win" situation.
Should there be no three-way agreement, the vote at the Lima session will be a straightforward selection of only the 2024 host city.