Paris 2024 chairman Tony Estanguet has said there will be "no Olympic and Paralympic Games in Paris in 2028" if their bid for the Games four years earlier is unsuccessful.
Calls for the International Olympic Committee (IOC) to award both the 2024 and 2028 editions to Paris and Los Angeles respectively have gathered pace in recent months.
The IOC contacted both Los Angeles and Paris following the decision of its ruling Executive Board last week to establish a working group to investigate the possibility of awarding both Games at its Session in Lima on September 13.
The panel is due to report during the IOC Candidature City Briefing taking place in Lausanne on July 11 and 12.
IOC members will have "discussions" there based on the recommendations.
It is widely assumed that, should the scenario emerge, then Paris would be awarded the 2024 edition and Los Angeles the 2028 Games.
The French capital has claimed that if it does not host the Games in 2024 then they will not be able to build on the land earmarked for the Olympic Village in Seine-Saint-Denis as it will not be available after that.
The possibility of awarding both Games follows a 2024 bid campaign which has seen three cities - Hamburg, Rome and Budapest - withdraw.
At a round-table event here in London today, Estanguet once again reiterated that Paris' bid is solely for 2024 and ruled out any notion that the French capital will consider hosting in 2028.
"We have only one objective and that is to host the Games in 2024," Estanguet said.
"We have built everything with this objective in mind.
"We only have the ability to hold the Games in 2024, our project is made only for 2024.
"There will be no Games in Paris in 2028.
"It was very clear with our partners and leaders that we are only bidding for 2024.
"Our project is not possible for 2028.
"This is the fourth bid of Paris.
"We believe we learned a lot from the previous bids and came back stronger than ever and now this is the last chance.
"It is now or never with Paris."
Los Angeles Mayor Eric Garcetti warned yesterday that his city is not going to give up on their campaign to host the 2024 edition of the Games either.
"We are competing for 2024," Garcetti told insidethegames in Los Angeles.
"I would love to visit my friends in Paris in 2028.
"We have never contemplated anything else."
When asked, Estanguet also claimed that it was not down to Paris to strike a deal with Los Angeles and that it would leave the politics of the decision to the IOC.
"It is not our job to find an agreement with Los Angeles," added the triple Olympic canoeing gold medallist.
"It is the IOC that carries this responsibility and our on side we have to follow the rules.
"We will see what happens in the coming weeks when we have an occasion to meet if the discussion will come.
"But, from our side, we do not have anything to negotiate."
An official statement from Los Angeles 2024 this evening has once again reaffirmed their commitment to hosting the Games in 2024, claiming to be the "right city" for the current climate.
"Los Angeles is the right city at this critical time for the Olympic Movement and is only bidding for 2024," read the statement.
"With all permanent venues already built and 88 per cent public support, only LA 2024 offers the lowest-risk and truly sustainable solution for the future of the Olympic Movement in 2024 and beyond."
A final decision is due to be made at the IOC Session in Lima on September 13.