Grand Slam tennis got its first experience of a video-assist review system at the US Open - but the moment of history was labelled a 'farce' by Andy Murray after the technology malfunctioned.

The official pulled out headphones to listen as she tried to watch an instant replay of the incident.

But, after a long delay, Engzell announced the video review was "not working".

"It took about four minutes to make a decision," said Murray, who was 15-30 down in a game where he was serving for the match.

"I'm pro using technology to get to the right calls - but you've got to have it working. When it goes like that, it turns into a bit of a farce."

The Swedish umpire was unable to see the replays on her tablet which meant she could not make a ruling, despite the big screens inside the Grandstand court at Flushing Meadows showing her, the players and the crowd what had happened.

"This is supposed to be the official feed," Engzell told the two players as she pointed to her personal screen.

"I have nothing here. VAR has stopped working."

Addressing the whole stadium, she said: "Unfortunately, the VR [video review] is not working, what you are watching here is from television so the original call stands."

US Open officials confirmed the dedicated on-court tablet had malfunctioned and stopped the reviewable video from being delivered.

"Per protocol, a video review and any call based off a review must be made by the chair umpire via the video delivered to their tablet on court," organisers said.

"If the video is not available on the chair umpire's tablet, the original call on the court stands.

"Immediately following the match, the malfunctioning tablet on Grandstand was repaired."

Technology has been a key part of tennis for many years to decide line calls but it is the first time the umpires have been able to access a video-assist review.

The US Open introduced the system for chair umpires to be able to immediately check incidents - double bounces, hindrance and a player touching the ball or the net - if they are challenged by a player.

"I knew there is VR, I don't know how they use it," said Murray, who levelled at 30-30 after the decision and went on to serve out the match in the same game.

"Maybe it wasn't on the umpire's tablet but it was on the big screens where they are showing multiple different angles and it is pretty clear from the second angle it had bounced twice.

"I don't know who makes the call because she said it wasn't available to her so went to the original call.

"I'm pleased the original call stood and I got the point."