MOSCOW - Brazilian football great Ronaldo and British pop star Robbie Williams will participate in Thursday's World Cup opening ceremony before the first match between hosts Russia and Saudi Arabia, FIFA announced on Monday.

Russian soprano Aida Garifullina will also take part in a revamped version of the traditional pre-tournament extravaganza at Moscow's Luzhniki Stadium, football's governing body said in a statement.

"The opening match is always a very symbolic one - it is that instant when you realize that the big moment you, as a player or fan, have been waiting for four years has finally arrived," said Ronaldo, a World Cup winner in 1994 and 2002.

Unlike previous editions, this year's opening ceremony will take place just half an hour before the curtain-raiser match, with a stronger focus on musical acts.

Some 80,000 fans are expected to be in attendance while millions more will watch the live broadcast around the world

"No one knows what will happen in the four weeks of the tournament, but everyone is sure that it will be memorable," Ronaldo said.

"Of course it is also an emotional one for the hosts. After so much hard work, suddenly the whole world is gathered in your backyard to celebrate their love for football. I felt that in Brazil four years ago and I am now happy to share this excitement with the Russians as well."

No details were given about the role Ronaldo will play in the ceremony, whose creative director is local producer Felix Mikhailov.

"We'd like to invite football and music fans to party with us in Russia, in the stadium, or to tune in their TVs a little earlier for an unforgettable show," Williams said.