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The US Open kicked off in New York on Monday but not as we know it.

It's the first time since the world was gripped by the coronavirus pandemic that one of the four major tennis tournaments - a Grand Slam - is taking place.

Several top names will not be playing at the tournament, although there is still plenty of star power in the form of Serena Williams, Novak Djokovic and Andy Murray.

The event is taking place inside a 'safety bubble' which includes regular testing and strict rules on movement of the players, their support staff and tournament officials.

"This is a really tough test for all the players. This is a US Open that we have never seen before," tournament director Stacey Allaster told the ´óÏó´«Ã½.

Defending champions Rafael Nadal and Bianca Andreescu are the biggest names missing from the competition because of their health and travel concerns.

Women's world number one Ashleigh Barty and Wimbledon women's champion Simona Halep will also not be playing.

Another big name not in New York is tennis legend Roger Federer, who is recovering from knee surgery.

The absence of Nadal and Federer gives an opportunity to men's world number one Novak Djokovic to close in on his rivals in the quest for the most Grand Slam titles.

Novak currently has 17 titles, two short of Nadal and three away from Federer's total of 20.

Andy Murray is the star British attraction as he continues to rebuild his career following hip surgeries.

The 33-year-old Scot is now ranked 134th in the world but is a former US Open champion, two-time Wimbledon winner and two-time Olympic gold medallist.

British women's number one Johanna Konta reached the quarter-finals at Flushing Meadows last year and goes into the tournament as a strong threat.

She will face fellow Briton Heather Watson in the first round.

Dan Evans, Kyle Edmund and Cameron Norrie are the other Britons in the singles.

Every person within the bubble has been twice tested for coronavirus on their arrival.

If a player tests positive during the US Open they will be withdrawn from the event in line with New York state guidelines.

Most players are staying in one of two hotels, although Djokovic and Williams are among the few to hire private residences.

Those homes have 24-hour security - paid for by the player - to make sure the bubble rules are not broken.

Line judges have been replaced by an electronic system on all courts except for the Arthur Ashe and Louis Armstrong main courts, while matches will have three ball kids instead of the usual six.

There are no qualifying rounds or mixed doubles, with the men's and women's doubles reduced to 32 teams and the wheelchair events taking place after initially being left out by organisers.

However, they will be competing in front of empty stands with no fans allowed at the tournament.