We'll be taking a short break now while we wait for Britain's Harriet Dart to get under way against France's Chloe Paquet.

They will follow Australia's Adam Walton and France's Alexandre Muller on Court 16, where the former has just taken the second set on a tie break to level the match.

It's tough to predict when that match will end but there are at least two sets still to come.

Sky's commentary team just estimated it might be an hour at least until we see Britain's Harriet Dart in action against France's Chloe Paquet on Court 16.

Australia's Adam Walton is currently 6-4 5-4 up against France's Alexandre Muller on that court now.

Dart will be hoping she fares better than fellow Briton Jan Choinski, who suffered a five-set defeat by Spain's Roberto Carballes Baena on the same court earlier today.

With Madison Keys ticking along nicely on Armstrong, it is a good chance to see what else is happening around the Billie Jean King National Tennis Center.

Over on Grandstand, there is a first-round match which fans will be queuing up to catch a glimpse of: irrepressible Frenchman Gael Monfils against diminutive Argentine Diego Schwartzman.

Schwartzman came through qualifying in what is the final Grand Slam of his career - and he's just taken the first-set tie-break.

Elsewhere, Bulgarian ninth seed Grigor Dimitrov is a set up against France's Kyrian Jacquet and Argentine 29th seed Francisco Cerundolo has levelled up at one-set each against Austria's Sebastian Ofner.

Another match to keep an eye on is Reilly Opelka against Italian 18th seed Lorenzo Musetti.

Opelka, the giant American with a ginormous serve, has been out injured for the best part of two years, but has returned to court during this American swing and wins the second set to level against the Wimbledon semi-finalist.

Madison Keys has broken in the second set with a rasping backhand which beats Katerina Siniakova.

It will take something special from the Czech to prevent American Keys from reaching the second round from here.

American 14th seed Madison Keys has taken the first set 6-4 against the Czech Republic's Katerina Siniakova on Louis Armstrong Stadium.

Keys achieved her best ever Grand Slam singles finish at the US Open when she finished runner-up in 2017 to Sloane Stephens.

We're one set closer to seeing Harriet Dart in action.

She's last up on court 16, where Australia's Adam Walton has just won the opening set 6-3 against Alexandre Muller of France.

Dart got to the second round of the US Open for the first time in 2022 and she'll be hoping to beat Frenchwoman Chloe Paquet today to do the same again.

Lorenzo Musetti has had a pretty good year.

He made the fourth round of a Grand Slam for the first time at June's French Open before reaching the semi-finals at Wimbledon a month later.

The Italian 18th seed also got his hands on Olympic bronze in Paris.

And it's so far, so good for Musetti at Flushing Meadows. He's just won the opening set 7-6 (7-3) against American Reilly Opelka over on court seven.

Image source, Getty Images

• Grigor Dimitrov, Frances Tiafoe and Holger Rune are among the men's seeds in first-round action.
• Wimbledon champion Barbora Krejcikova starts her US Open campaign against Marina Bassols Ribera, while Great Britain's Harriet Dart plays France's Chloe Paquet last today on Court 16.
• Defending men's champion Novak Djokovic and last year's women's runner-up Aryna Sabalenka play on the show courts during the evening session.

With Ben Shelton and Coco Gauff whizzing through their matches on Arthur Ashe Stadium, there's a bit of a lull now until the evening session.

That doesn't get under way until midnight here in the UK.

Sloane Stephens, the 2017 US Open champion, opens the evening session against France's Clara Burel.

That's followed by Novak Djokovic, a four-time winner in New York, taking on Radu Albot of Moldova.

BBC Radio 5 Live

Coverage of the US Open is, for the next hour or so, on BBC Radio 5 Live.

Click on the link at the top of this page to listen live.

Image source, Reuters

If you're clicking on this page for the first time today, let's bring you up to speed with what's happened so far at the US Open today:

• Defending women's champion Coco Gauff cruised to a 6-2 6-0 win over Varvara Gracheva.
• Olympic champion Zheng Qinwen, Paula Badosa, Elina Svitolina and Daria Kasatkina are all safely through to round two, but ninth seed Maria Sakkari retired injured from her match after losing the first set to Wang Yafan.
• Great Britain's Jan Choinski was beaten in a five-set thriller with Roberto Carballes Baena.
• Dominic Thiem's Grand Slam career is over - the Austrian, who won the 2020 US Open and is retiring later this year, lost in straight sets to 13th seed Ben Shelton.
• Through to the second round of the men's draw are Alexander Zverev, Taylor Fritz, Casper Ruud and Matteo Berrettini.

Still to come on day one... GB's Harriet Dart, Novak Djokovic and Aryna Sabalenka

David Law
Commentator on BBC Radio 5 Sports Extra and BBC Sounds

Speaking before the start of play about the women's draw:

Elena Rybakina has had a lot of injury and illness this year. Iga Swiatek has had a bit of a drought by her standard in terms of results.

Coco Gauff does look out of form. It's going to be fascinating to see whether the memories from [winning] the US Open will help her. She's a great match player but nobody is in dynamite form, I think it really is only Aryna Sabalenka and yet the conditions are different here so it's fascinating to me.

I think we could see something really surprising.

More from Coco Gauff about the TikTok comment that changed her outlook: "Someone commented on my TikTok saying you've won in life, literally and figuratively, and there's no point in piling pressure on yourself on a victory lap.

"I'm just treating this tournament like that and if you defend something that means you won something. If you did it that means you can do it again, so whether I do it again this year or not, I am going to do it again - whether it's 2024 or not, I will do it again."

Defending champion Coco Gauff speaking after her first-round win over Varvara Gracheva: "There's definitely a lot of pressure this tournament but I'm just enjoying it. Last year was incredible so I'm just bringing those vibes - whatever happens, happens. It's an honour to be back on Arthur Ashe playing in front of you guys.

"If I played this last week I feel like it would be really difficult, but my perspective has changed a lot over seven days. I was just trying to enjoy the match. I enjoyed it today and obviously it was straightforward, but even if it was tighter these are the moments you live for. I am just happy to be back on this court and playing like I did.

"I know the last few weeks have been a little bit tough and I think this has been the best tennis I have played in a while."

Image source, Reuters

The last time Coco Gauff met Varvara Gracheva was in the quarter-finals of the Auckland Classic back in January.

The American emerged as the victor then, too, and went on to win the tournament.

A good omen, perhaps?

Naomi Broady
British player on BBC Radio 5 Sports Extra and BBC Sounds

How is Roberto Carballes Baena going to recover before his next match? It has been an incredible effort for him. He's never reached the third round, is he going to have enough energy to do that here?

Jan Choinski couldn't have put any more out there, it was a great fight from him. I hope he doesn't have too many regrets from the match, especially not taking those break point chances early on in the fifth.

The fact that he was able to turn it around and get himself back into it is all credit to him. With his work ethic and the fight that he has shown out there on court today, hopefully good things are to come.