Match officials explaining VAR decisions live to stadiums and television audiences for Women's World Cup games will make the process "more transparent", FIFA's referee chief Pierluigi Collina said on Tuesday.

The concept will be used at a major tournament for the first time when the World Cup starts on Thursday, having been trialled at the men's Club World Cup in Morocco this year and the men's U20 World Cup in Argentina last month.

Collina, chairman of the FIFA Referees Committee, told reporters that there had been positive feedback from the trials.

"We want to give more transparency, more understanding of the decision made by the referee," the Italian said.

"The referees here in Sydney have already practised at the training grounds using the PA system and things are going well.

"We are very confident this new tool will be very positive."

Fans have long called for more transparency over VAR (video assistant referee) decisions.

Match officials at the World Cup in New Zealand and Australia will consult a screen on the side of the pitch before relaying their decision, the reason for it, the players involved and a brief description of the incident through the PA system via a microphone on their shirt.

Collina admitted to some trepidation with referees required to explain in English, which is not the mother tongue for many, adding extra pressure.

"In anything there are pros and cons," he said. "After we will discuss and consider what is best for the future."

Referees are also under instruction to clamp down on time-wasting at the World Cup.

mp/pst