The giant opening ceremony extravaganza that Paris is planning to hold on the River Seine to launch next year’s Olympic Games could be moved if France is hit again in the run-up by extremist attacks, French President Emmanuel Macron said.

Mr Macron’s comments in a television interview on Wednesday night were a rare behind-the-scenes glimpse into the deep layers of planning for the July 26 ceremony.

Many details about the show remain shrouded in secrecy to preserve its hoped-for wow factor. The security, with tens of thousands of police and soldiers deployed, will be intense.

The athletes will be paraded through the heart of the French capital on boats on the Seine for the first Summer Games opening ceremony held outside a usual stadium setting. Both banks of the river will be lined by hundreds of thousands of spectators.

“We are preparing an opening ceremony that is unique, which I hope will make the French very proud,” Mr Macron told public broadcaster France 5.

“It will be a moment of beauty, of real art, of celebrating sport and our values, with the Seine and the capital as the theatre.”

But he said plans could be revisited for security reasons. He cited deadly extremist attacks that hit Paris in 2015 as an example of the type of severe crisis that could force a rethink.

“You’re 15 days from the Olympic Games. You have a series of terrorist attacks. What do you do? Well you don’t organise (a ceremony) on the Seine,” he said.

“Since we are professional, there are obviously plan Bs, plan Cs, et cetera.

“You have to be prepared for everything,” he added. “If there’s a surge of international or regional tensions, if there is a series of attacks … that’s a plan B.”

Speaking at an end-of-year news conference on Wednesday, before Macron’s subsequent TV interview, chief Paris Games organiser Tony Estanguet said the Seine ceremony is “the only project that we are working on”.