Five Britons in first-round action on day three in New York
LIVE: Billy Harris 4-6 Felix Auger-Aliassime
LIVE: Fran Jones 0-6 Germany's Eva Lys
Sonay Kartal also out after 6-3 1-6 6-1 defeat by Beatriz Haddad Maia
Jacob Fearnley takes on Roberto Bautista Agut later on Tuesday
Men's defending champion Jannik Sinner beats Vit Kopriva 6-1 6-1 6-2; Iga Swiatek wins 6-1 6-2 against Emiliana Arango
Listen to BBC Radio 5 Sports Extra coverage at top of page (UK only)
*Sinner 4-0 Kopriva
Jannik Sinner is on a 21-match winning streak in hard-court Grand Slams - it's a tough ask for Vit Kopriva, who has never played a main-draw match at the US Open before, and finds himself on Arthur Ashe Stadium playing the world number one.
The Italian holds serve to love and then breaks Kopriva to love.
The top seed hasn't quite found his service rhythm yet but already he's a double-break up.
Haddad Maia 6-3 1-6 6-1 Kartal
The three British players that were in singles action on the first two days of the US Open made it safely through to round two, but the two Britons we've seen so far today have been beaten in their first-round matches.
Fran Jones, Billy Harris and Jacob Fearnley are in first-round action later today.
Haddad Maia 6-3 1-6 6-1 Kartal
Image source, Getty ImagesSonay Kartal's US Open main-draw debut ends at the first hurdle.
Having forced a decider, the British number three was clearly hampered by something in the final set - either cramp or an injury which severely restricted her movement at times.
Beatriz Haddad Maia had her own physical problems to contend with in the third set, struggling to move on occasions, but the Brazilian 18th seed is through to round two.
*Haddad Maia 6-3 1-6 5-1 Kartal
Sonay Kartal hits a forehand winner.
Beatriz Haddad Maia with a double fault.
Two match points saved.
*Sinner 2-0 Kopriva
Jannik Sinner is taken to deuce in his opening service game but holds comfortably.
The Italian, wearing the elbow sleeve that he has sported since Wimbledon, had to pull out of the Cincinnati final against Carlos Alcaraz last week with illness, which he says he has now recovered from.
And he looks in good shape as he immediately earns two break points on Kopriva's opening serve - one is enough.
Image source, Getty Images*Haddad Maia 6-3 1-6 5-1 Kartal
Two match points for Beatriz Haddad Maia on her own serve.
*Haddad Maia 6-3 1-6 5-1 Kartal
Leon Smith
GB Davis Cup captain on BBC Radio 5 Sports Extra and BBC Sounds
If any young players want to look at how to react through ups and downs, have a look at Haddad Maia, she's constantly positive, making positive engagement with her team whether losing or not.
She's moving fine now - amazing fight and heart from her.
*Haddad Maia 6-3 1-6 5-1 Kartal
Beatriz Haddad Maia gets it done this time, sending a return down the line for a winner.
She will serve for the match now.
Image source, Getty ImagesHaddad Maia 6-3 1-6 4-1 Kartal*
Into a fourth deuce in Sonay Kartal's service game - just what both players would have wanted with their bodies creaking.
To be fair, both are moving a little bit better now.
Beatriz Haddad Maia has a fourth chance to break in this game but Kartal holds firm as the Brazilian finds the net.
But hang on - here's another break point...
*Sinner 0-0 Kopriva
We're under way on Arthur Ashe Stadium as world number one Jannik Sinner opens his US Open campaign against Vit Kopriva of the Czech Republic, who is making his debut at this Grand Slam.
Image source, Getty ImagesMusetti 6-7 (3-7) 6-3 6-4 0-0 Mpetshi Perricard*
Tenth seed Lorenzo Musetti is looking in good shape against Frenchman Giovanni Mpetshi Perricard, wrapping up the third set to take a firm hold of the match.
World number 37 Mpetshi Perricard is famed for his booming serve but Musetti has broken him twice in the match so far, without yet facing a break point himself.
It's been a miserable couple of months for Italian Musetti, who struggled with injury after reaching the semi-finals of the French Open, but he is looking back to his best on Louis Armstrong today.
Image source, Getty ImagesHaddad Maia 6-3 1-6 4-1 Kartal*
Beatriz Haddad Maia wins a couple of points at the net to get to 15-30 on Sonay Kartal's serve, before the Briton sends a forehand wide.
Two points to restore that double break... but Kartal saves them both in style.
Break point number three quickly follows, however, the Brazilian's forehand drifts wide.
Haddad Maia 6-3 1-6 4-1 Kartal*
Katie Smith
Presenter on BBC Radio 5 Sports Extra and BBC Sounds
Haddad Maia is trying to urge herself on but her legs won't move, this is a chance for Kartal.
Sonay is moving fine now. If she can just play to 70% of her movement she can win this match.
Do you believe in miracles, Sonay Kartal? Because there might be one in action here.
Haddad Maia 6-3 1-6 4-1 Kartal*
Well, well, well...
Sonay Kartal is hardly full of energy but suddenly looks the more sprightly of the two players.
Beatriz Haddad Maia seized up completely after the first point of that game and is almost playing walking tennis for the rest of it.
*Haddad Maia 6-3 1-6 4-0 Kartal
Abigail Johnson
Commentator on BBC Radio 5 Sports Extra and BBC Sounds
Unbelievable! The Brazilian is now pointing to her leg. What is going on here?!
You've never seen scenes like this in the first round of a Grand Slam. It's now hampered player against hampered player.
*Haddad Maia 6-3 1-6 4-0 Kartal
Goodness me - now Beatriz Haddad Maia pulls up as she chases a ball to the net. Both players are really toiling out there on Court 12 and both are struggling to make more than a couple of steps into the ball.
Not sure I've seen anything like this before.
*Haddad Maia 6-3 1-6 4-0 Kartal
Leon Smith
GB Davis Cup captain on BBC Radio 5 Sports Extra and BBC Sounds
Haddad Maia has just got to play a simple strategy now, just play open court and be relentless with that, keep making Sonay move as much as possible.
Sonay is not driving on her serve. I'm surprised she hasn't called for her trainer yet.
*Haddad Maia 6-3 1-6 4-0 Kartal
Sonay Kartal is really struggling. She can hardly move around the court and loses her serve to love.
She's a double break down now and this match is slipping away quickly.
Such a shame after Kartal fought back so well in the second set.
Jonathan Jurejko
BBC Sport senior tennis reporter at Flushing Meadows
Image source, BBC SportSeeing as Mander the Maltipoo has just taken centre stage, I might as well show you dog lovers this.
Named after a combination of the first names of Marta and her coach Sandra Zaniewska, Mander goes everywhere with the Ukrainian player - including our interview a couple of days ago.
Mander was content to sit in the shade under the table as we chatted.
Then insisted on posing for a photo with mum.
Boulter 4-6 4-6 Kostyuk
Image source, Getty ImagesMarta Kostyuk speaking to Sky Sports after her win on Grandstand: "First of all, thank you guys for your support. It is my first ever win on this court. I'm really happy to close out this win after missing a number of match points."
On losing to Katie Boulter in the 2024 San Diego Open final: "That one was really tough. I can still remember that match and she was playing unbelievably well. It is a different day and a different year now, and it shows everything changes in tennis. I'm really glad I got this one."
On bringing her dog - Mander the Maltipoo - to this year's tournament: "He had a haircut yesterday. He is our biggest trophy, for sure. It is amazing to be able to travel with him. It is preparation for parenting for us. My team are also obsessed with him, so if I need a break then they are always happy to take him."
