JEONJU -- FIFA's top refereeing official emphasized Friday that the video review system at the upcoming youth tournament in South Korea will only be used in "clear mistakes."

The 2017 FIFA U-20 World Cup, which runs from Saturday to June 11 in six South Korean cities, is the first youth tournament by the world football governing body to rely on the video assistant referee system. FIFA previously used the VAR system at the Club World Cup in Japan last November.

In a press conference Friday, FIFA's Head of Refereeing Massimo Busacca said he doesn't want the VAR system to be used in every play of the game.

"We're talking only about clear mistakes and something that can really change a lot in this competition," Busacca said at Jeonju World Cup Stadium in Jeonju, North Jeolla Province, where the official opening match of the U-20 World Cup will be staged. "I strongly recommend referees don't look into every single situation of the game."

FIFA previously explained that the VAR system will help referees when important situations occur during the match, such as goals, penalty decisions, direct red cards and cases of mistaken identity. Busacca said if the VAR system is used in "normal situations," it will hurt the nature of the sport.

"If we open this door, we will kill football," he said. "We'll see only 20 minutes, instead of 50 minutes (of actual playing time), especially in the championship matches where you have a lot of provoked contacts."

For every match at the U-20 World Cup, there will be two VARs. They will be given access to all broadcast feeds inside a video operations room, and will give information to the referees on the field if such situations occur. FIFA has appointed a total of 22 VARs for the U-20 World Cup.

"The group of VARs have the same level as the referees who are on the pitch," he said. "They are top referees and are candidates for refereeing the most important competitions of FIFA."

Busacca, a former referee from Switzerland, said with various camera angles and video feeds, he believes decisions from the video review will not take much time at this U-20 World Cup. But even if it takes long, he insisted that making correct calls is the most important task.

"I prefer having 10 seconds more," he said. "At the end, what's really important is that the result should be correct."

Johannes Holzmuller, FIFA's Head of Football Technology Innovation, said the video review system staff are trying to give quick information as soon as possible and that it's an area it is looking to improve.

"I can tell you from (Club World Cup) matches in Japan and other leagues that time really depends on the incident," he said. "If there is a clear mistake, we need only a short amount of time. In Japan, on average it took about one minute and a half or two minutes (to make a decision from video review), but we hope to improve." (Yonhap)