Olympic chief Thomas Bach said on Sunday the IOC faced "very important decisions" as the vote on awarding the 2024 and 2028 Games simultaneously loomed in Lausanne.
Paris is battling with Los Angeles for the right to succeed 2020 hosts Tokyo and stage the Games in seven years time.
But last month IOC bosses backed a plan to award both Games together, with the recommendation expected to be backed by a vote at their Swiss headquarters on Tuesday.
Bach opened a ground-breaking week for the Olympic movement telling IOC top brass: "We'll have some interesting days in Lausanne. Some very important decisions will be taken. More decisions will be made in Lima."
The Peruvian capital Lima hosts the 130th IOC Congress on September 13 where the vote to decide the 2024 and likely 2028 hosts will be made.
Both Paris, whose delegation is being led by French President Emmanuel Macron, and Los Angeles will present their bids to the IOC on Tuesday.
Last week the IOC Evaluation Commission report lavished praise on both bidding cities, stating there was "very little to separate" the two bids.
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