Which city will host which Games is undecided for now, with both preferring 2024.
All the 83 attending IOC members at the 130th IOC session voted for the decisions made by the IOC Executive Board in early June, saying they will next seek a "tri-partite" agreement.
That could mean either that one city will accept the 2028 Games before an IOC session in September or that each would be willing to accept 2028 if it is not awarded the 2024 Olympics.
Los Angeles and Paris are the only bidders for the 2024 Olympic Games after several cities, including Oslo, Rome, Budapest and Munich, withdrew their bids.
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.
