"I like to compare it with a football team, with a player, the referee knows the responsibility, knows how important [it is] to show to everybody that they know what they are doing... As every football team we are ready for this competition," Busacca said.

Chairman of the FIFA Referees Committee Pierluigi Collina said that for the first time a "mini-tournament" had been organized with eight local teams specially for the referees to practice ahead of the World Cup.

"As I told the referees this morning... There is not anymore time to speak, to talk, now is time to act. So they are very eager to start with the kick-off of the first match," Collina added.

He also said that the most important thing for the referees was to protect the image of the tournament and ensure the players' safety.

Russia will host the FIFA World Cup from June 14 to July 15, with the games set to be held in a total of 11 cities.

The tournament will kick off at Moscow's 81,000-seater Luzhniki Stadium on Thursday, with the host nation facing Saudi Arabia.