French President Emmanuel Macron says the Paris Olympics opening ceremony could move from the River Seine if the security risk is too high, reports BBC News.
Mr Macron said it could be "limited to the Trocadéro", across the Seine from the Eiffel Tower, instead of covering the planned stretch of the river.
He added that it could even be moved to the Stade de France, reverting to a traditional ceremony.
The opening ceremony is set to be the first to be held outside a stadium.
More than 10,000 athletes are expected to sail along a 6km stretch of the Seine on some 160 barges.
The organisers had originally planned to accommodate some 600,000 people to watch the ceremony from riverbanks, but that has now been scaled down to 300,000 people.
It has already been revealed that tourists will not be given free access to watch the ceremony, as was originally planned. Instead, tickets will be by invitation only, not via open registration.
"This opening ceremony... is a world first. We can do it and we are going to do it," Mr Macron said in an interview with French media outlets BFMTV and RMC.
But for the first time, he admitted that there were back-up plans in place.
"There are plan Bs and plan Cs", he said, adding: "We are preparing them in parallel, we will analyse this in real time."