British Olympic Association chief executive Andy Anson has expressed "concerns" over the opening ceremony for the 2024 Paris Games on the river Seine after French President Emmanuel Macron said it could be moved to a stadium in the event of a security threat.

Macron, speaking on Monday, said for the first time that instead of teams sailing down the Seine on barges, the ceremony could be "limited to the Trocadero" building across the river from the Eiffel Tower or "even moved to the Stade de France".

The Paris organisers have devised a ceremony that is unprecedented in Olympic history as it breaks from the tradition of the Games opening in the main stadium.

The current plans would see as many as 10,000 athletes sailing along a six-kilometre (four-mile) stretch of the Seine in around 160 barges, before gathering at the Trocadero for a ceremony.

But with war currently raging in Ukraine and in Gaza, concerns have been raised that the ceremony could leave athletes potentially vulnerable to attack.

"I'm clearly concerned," Anson told Sky News in an interview broadcast Wednesday to mark 100 days to go until the opening ceremony on July 26.

"It's one of the most important things that we have to manage from a risk perspective.

"We'd be naive if we weren't thinking about that. Our number one priority is to keep all our athletes, our broader entourage and our fans safe."

Anson added the opening ceremony "is a high-risk environment and that's got to be managed accordingly, but the French are very, very aware of that".

Macron said the opening ceremony would take place under high security, but that organisers had contingency plans.

"This opening ceremony... is a world first. We can do it and we are going to do it," Macron said in an interview with BFMTV and RMC.