The US Department of Homeland Security has granted athlete waivers to players and support personnel, meaning that non-US nationals can enter the country regardless of their home country and previous travel movements - but it is not yet clear whether there will be any quarantine requirement for those entering the US.
The situation is complicated by the rescheduled French Open taking place immediately after the US Open - with qualification beginning a week after the New York final, and the main draw action starting on Sunday September 27.
It is possible that those travelling from the US back to Europe would be required to self-isolate for a period of up to two weeks as well - meaning that at the current time many will have to choose between the two Slams.
LIKELY TO PLAY
Serena Williams, chasing that elusive 24th Grand Slam title, will play - fitness permitting. She has been in the media spotlight recently as she, husband Alexis Ohanian and daughter Olympia were revealed as part-owners of new soccer club Angel City FC.
US Open: Serena Williams favourite to win record-equalling Slam
Novak Djokovic, after expressing his dissatisfaction with the rules laid down by the US Open, backed down a little, enthusing exclusively to Eurosport: "I think that a lot of people were sceptical, especially for the US events considering what the US went through as a country during this pandemic. So a lot of people, including myself, were quite sceptical on whether it would happen or not. We are very glad that it is happening, of course, and it is very important that we provide opportunities, we provide jobs, we provide opportunities for players to compete."
Former champion Andy Murray says he intends to play as long as everyone's safety can be guaranteed, writing in his BBC column: "Playing at a behind-closed-doors US Open is something I intend to do - as long as it is safe." On Monday the former world number one was confirmed as a wild card for the Western and Southern Open, and the 33-year-old has since been handed a wild card for Flushing Meadows - as has former champion on the women's side Kim Clijsters.
The 2019 men's runner-up Daniil Medvedev is also likely to play - and has been spotted in training and confirmed for the Western and Southern Open.
Of the men's top 10, all are European, but only the injured Roger Federer is not currently down to play the warm-up event. Stefanos Tsitsipas, David Goffin, Matteo Berrettini and Dominic Thiem are all likely to head to the USA following their Ultimate Tennis Showdown showings in the south of France - although Berrettini for one has gone on the record saying although he would like to play in the USA his health is his priority and he will make a decision nearer the time.
The same conclusions could be drawn from looking at the WTA entry list for the Western and Southern Open. As well as Serena, top 10 players Karolina Pliskova, Sofia Kenin and Belinda Bencic are down to play the event, along with two-time Grand Slam champion Garbiñe Muguruza and Naomi Osaka, who took a wildcard into the event.
Although Bencic recently gave an interview saying that she is very aware of the health risks in the USA, she has since withdrawn from the European tournaments she was entered in throughout August.
Defending champion Bianca Andreescu is on the US Open entry list, but is currently not registered to play the Western and Southern Open or any other warm-up event. However, the Canadian has previously expressed cautiously positive views about playing in New York, writing on Twitter in June: "I have no doubt that the USTA has come up with the best plan to insure our safety as we look to the return of tennis in 2020," adding: "I plan to make the most of the opportunity to get back on the court."
British number one Johanna Konta has withdrawn from the clay-court Ladies Open Palermo and entered the Top Seed Open in Lexington followed by the Western and Southern Open. She took part in the second instalment of Jamie Murray's Battle of the Brits tournament, which suggests she may now be concentrating on hard-court practice and leaving the clay season aside for this year.
Roger Federer is still recovering from injury and will not play again this year, while another former French Open champion, Stan Wawrinka, is not on the US Open entry list and has been seen practising on clay, suggesting he will focus on the French Open.
Melbourne tournament director and Tennis Australia CEO Craig Tiley certainly hinted at that in an interview when he said: "All of them I've spoken to – there's not one that hasn't – are looking to the beginning of 2021 and the beginning of the new season as the new hope for tennis globally. I personally think that some of the top players will be in doubt [for the rest of 2020] and that's simply because they may feel it's too soon. It's nothing against the US Open."
It seems massively unlikely that Tiley would not have spoken to Australia's biggest sporting star as he gauged the tennis community's plans for the rest of the year.
He added: "It hurts me at my core not to be out there competing in one of the sport's greatest arenas, Arthur Ashe Stadium."
Reigning Wimbledon champion Simona Halep, who is also a former Roland Garros winner, is on the US Open entry list but has said she will stay in Europe, and at this stage is unlikely to go to New York. The Romanian is very cautious when it comes to travel - having opted not to play in the 2016 Rio Olympics due to the risk of the zika virus.
Tennis Legends: Players 'must be asked' about tennis return - Halep
Halep confirmed her intent to participate in the WTA tour events in Europe throughout August, with other entrants including former French Open champion Jelena Ostapenko (who will play in Palermo from August 3) and one-time Wimbledon finalist Eugenie Bouchard. It seems more than likely that they will stay in Europe ready for the French Open rather than cross the Atlantic again. Ostapenko is on the US Open entry list but had previously said she will not be going to the USA, while Bouchard would need to go through qualifying in New York as she is not ranked high enough to get a place in the main draw entry list.
Kiki Bertens of the Netherlands has said she will not be going to the USA for any events this year, according to her own government's advice about entering two weeks of quarantine on return. She has previously had great success on clay so not risking the French Open makes sense.
The Ukraine's Elina Svitolina has confirmed she will not be playing.
Katie Boulter has also said she will not be at the US Open, saying: "I haven’t put an entry in. I am very cautious as there is a pandemic going on. I don’t think it’s the right time."
China's number one Wang Qiang has withdrawn from the Western and Southern Open as well as the US Open, citing travel restrictions and safety concerns, as has recent Ultimate Tennis Showdown champion Anastasia Pavlyuchenkova.