Thousands of Olympic competitors cruised down the River Seine in a spectacular opening ceremony for the Paris Games on Friday that celebrated French history and culture to the delight of a crowd undeterred by persistent rain.

Nadal, a singles gold medallist at the 2008 Olympics, is playing in his final Games having also won doubles gold in Rio in 2016, while Djokovic was a bronze medallist in singles in 2008.

The Italian said he was "sad and disappointed" to drop out, adding that he had started feeling unwell on Monday after a practice week in Monaco.

France deployed about 1,000 police officers backed by Israel's own internal security service, Shin Bet, to welcome thousands of supporters for the evening kick-off. They cordoned off the streets around the Parc des Princes in western Paris and set up a perimeter a few kilometres away from the stadium

"I can't explain what happened. We spent about an hour and a half in the dressing room where they never told us what was going to happen," Mascherano told reporters.

The dealers have promised a steady supply of wares, but warned prices may go up and delivery wait times too under the weight of tens of thousands of security forces and heavy demand.

World Champions Argentina will be in action on day one as they take on Morocco in the opening match, starting at 7pm (Bangladesh Time)

The 37-year-old, a two-time Olympic champion, is planning to play in the singles and doubles at his fifth Games.

The ceremony, staged for the first time outside a stadium, will involve around 80 boats ferrying international athletes on a six km (3.7 mile) route along the river Seine towards the Eiffel Tower, said the official, Lambis Konstantinidis.

Both players had indicated their desire to participate in the Paris Games, but their Spanish clubs -- Real Madrid where Mbappe, 25, is set to play next season and Atletico for 33-year-old Griezmann -- have said they will not release them.

Iraq will join Japan and Uzbekistan at the Paris Games.

"The Olympic flame that we are lighting today symbolises this hope for a better future," said International Olympic Committee President Thomas Bach.