Paris (AFP) - The Paris Olympics were poised to open in a unprecedented ceremony along the River Seine on Friday as forecast rain threatened to dampen anticipation for the global sporting spectacular.

In an ambitious, high-risk departure from past opening ceremonies, up to 7,500 athletes were poised to sail down a six-kilometre (four-mile) stretch of the Seine in an armada of 85 boats.

Despite the rain that forecasters say is likely to fall during the ceremony, and a wave of attacks which paralysed France’s rail system early Friday, organisers were confident of pulling off the audacious opening extravaganza.

Basketball superstar LeBron James, who will be one of two Team USA flagbearers along with tennis star Coco Gauff, was seen being equipped with a clear plastic poncho to protect him from the predicted deluge.

“We’ll see tonight… but the closer it gets the more the models suggest we’re likely to get rain,” chief Games organiser Tony Estanguet told France Inter radio, while adding that there would be some modifications to the show if it was wet.

“It’s going to be a beautiful moment, it’s going to be a great party,” he added.

- Hunt for culprits -

French security forces are on their highest alert to prevent terror attacks spoiling the start of the first Olympics in Paris in 100 years, while acts of sabotage from hostile foreign powers were also a known risk.

French officials refused to comment on the identity of those responsible for the rail sabotage who appear to have had a sophisticated understanding of the network.

Far-left French anarchists have a history of targeting the train network with arson attacks.

Suspicions might also fall on Russia, which French President Emmanuel Macron has said in the past was planning to target the Games.

Commenting on the rail disruption, which will affect 800,000 people over the weekend, International Olympic Committee president Thomas Bach told the media he had no concerns.

“We have full confidence in the French authorities,” he said at the Athletes’ Village.

- Security blanket -

Compared to the Covid-blighted 2020 Tokyo Olympics, which were delayed by a year and opened in an empty stadium, the Paris opening ceremony will take place in front of 300,000 ticketed spectators and many more from overlooking buildings.

It will be the first time a Summer Olympics has opened outside the main athletics stadium, a decision fraught with danger at a time when France is on its highest alert for terrorism.

Thousands of spectators faced long queues and ticketing problems as they arrived at access points for the opening ceremony.

Many gates opened an hour late as staff had not yet been equipped with scanners to check tickets.

“The police have been amazing, but the organisation sucks,” said Michael Ohoven, 48, a German film producer, who paid 2,700 ($2,930) euros per ticket for him and his wife.

After passing scanners and checkpoints, the first arrivals discovered the numerous floating stages installed in the river channel and bridges that have been festooned with flags and the pink-and-purple colours of the Games.

“The atmosphere is really friendly,” said 75-year-old Frenchman Jean-Yves Herve who will watch with his grand-daughter.

“There are lots of foreigners, we’re enjoying it. It’s good for France.”

A huge security perimeter has been erected along both banks of the Seine, guarded around the clock by some of the 45,000 police and paramilitary officers who will be on duty on Friday evening.

Another 10,000 soldiers are set to add to the security blanket along with 22,000 private security guards.

“Without any doubt, it is much more difficult to secure half of Paris than to secure a stadium, where you have 80,000 people and you can frisk them and send them through turnstiles,” Frederic Pechenard, an ex-director general of the French police, told AFP.

Police snipers are set to be positioned on high points along the river, which is overlooked by hundreds of buildings.

The line-up of performers is a closely guarded secret but US pop star Lady Gaga and French-Malian singer Aya Nakamura are rumoured to be among them.

US rapper Snoop Dogg carried the Olympic torch earlier Friday, sparking speculation he might also appear in the ceremony.

Around 3,000 dancers are set to perform from the banks of the river and monuments including Notre-Dame cathedral in a show that will promote diversity, gender equality and French history.

The landmarks and architecture of the City of Light are set to feature as a backdrop both to Friday night’s show and much of the sport afterwards.

Paris’s vision is for a more cost-effective and less polluting Olympics than previous editions, with competitions set to take place at historic locations around the capital.