Officials at the French presidency and French Olympic Committee told The Associated Press on Tuesday that Valls' backing for the world's fair does not mean that Paris would be unable to bid for the Olympics.
While France's economic recovery is the top priority of Valls' government, the two projects would require huge funding that has yet to be finalized. But Nathalie Iannetta, the sports adviser to French President Francois Hollande, said both events could be pursued at the same time.
"The investments that will be made will benefit both projects," she said in a telephone interview.
Bernard Lapasset, who heads the French Committee for International Sport, said the proximity of the two events could even be an asset for France.
"We'll obviously need to be careful with the finances, but look what happened with Japan," Lapasset, who also heads the International Rugby Board, told the AP. "They won the rights to host the rugby World Cup in 2019 and the 2020 Olympics."
Bids for the 2025 expo are due in 2016, with a vote in 2018. Bids for the Olympics must be submitted next year, with the IOC vote in 2017.
Paris is one of several cities that have expressed interest in hosting the 2024 Games. Cities in the United States, Italy, Germany, South Africa, Qatar, Hungary and Turkey are among potential contenders.
Iannetta said the results of a feasibility study by the French Olympic Committee due early next year will be crucial in deciding whether Paris should bid for the games.
"If it shows that a Paris bid is pertinent and that we have good chances to win, then the World Expo bid won't be an obstacle," Iannetta said.
The French Olympic Committee issued a statement saying the feasibility study was being conducted by leaders from the sporting, political and business worlds working together "on a common road map."
A first hint on whether Paris might bid for the games is expected to come on Nov. 4, when the conclusions of 12 workshops on the issue will be made public. Organizers will then need to examine the financial issues.
Lapasset added that the outcome of the International Olympic Committee session in Monaco in December will be carefully taken into account before a decision is made. IOC President Thomas Bach is proposing changes to the bidding process as part of his package of "Olympic Agenda 2020" reforms.
By 2024, it will have been 100 years since France last staged the Summer Olympics in Paris in 1924, but Lapasset insisted this is not a good enough reason to put a bid forward.
"Everybody wants the games," Lapasset said. "But this won't be the reason behind a bid. We will only go ahead if there is a place to take."
Paris was considered the favourite in the bidding for the 2012 Olympics but lost out to London. Paris also was unsuccessful in a bid for the 2008 Games, which went to Beijing.
France decided not to bid for the 2020 Olympics after the French bid from Annecy was humiliated in the race for the 2018 Winter Games, receiving only seven votes in an election won by Pyeongchang, South Korea.
French President Francois Hollande has said he would back a 2024 Paris bid only if "all the conditions of success are present."