ST. PETERSBURG, Russia — Refereeing at the Confederations Cup in Russia may have been chaotic at times, but Video Assistant Referees have prevented major mistakes from being made, football's governing body says.

FIFA's head of refereeing Massimo Busacca says video reviews have not always looked good in tests at the tournament and admitted "many aspects should be improved" including faster, clearer communication after slow reviews have confused players, coaches and fans.

"We are certain that this can reduce refereeing errors," Busacca told a news conference. His choice of words suggests eliminating errors completely at the World Cup is too tough a goal.

"We are convinced if used correct(ly), it can reduce many mistakes. But not eliminate. We are here only to reduce," he said.

The former international referee said that communications between referees and the video assistants sitting in a darkened room outside the stadium needed serious improvement.

Match officials have complained of video assistants shouting loudly and at the same time into the referee's ear piece during games, a verbal assault that does not help clear decision making.

The former World Cup referee says he is positive about the new system being approved for use at next year's tournament in Russia.

Busacca insists the most important point at the two-week rehearsal tournament is that technology helped referees avoid major errors in 12 games so far.

FIFA research cites video replays helping referees overturn six "game-changing decisions." Referees' judgment in a further 29 "major incidents" was confirmed correct on review.

Busacca says FIFA must convince more member federations to help by using video reviews in their national competitions.

"We need our team, our referees, in member associations to do it every day."

He expressed irritation that referees in Russia were being criticized when they had only had five days to prepare and member federations were hesitating to use the technology.

He said it was crucial that referees had deep exposure to working with VARs before next year's World Cup in Russia, where the technology is expected to be used.

The change in refereeing, he said, was fundamental, with science replacing emotion. "Up until now decision are made in the heat of the moment. This is a new way to decide, without emotion."

Busacca rejected charges that weaker referees were being used at the Confederations Cup and that they were less able to deal with more senior Video Assistants.

He said he was appalled by the behaviour of Mexican and New Zealand players who became involved in a mass confrontation toward the end of their game.

The referee could have sent several players off. "Don't blame the referee. Blame the players. That is terrible behaviour," he said. Players were already learning how to abuse the video referee system by surrounding referees and putting pressure on them to consult the VAR.

"For now, it's not good looking. But at the end the honesty is good."

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Graham Dunbar in Sochi contributed to this report.