And there's the double break. Varvara Gracheva had the whole court to aim for, but her overhead smash flies long.

Coco Gauff is one game away from the first set. She's just about crept through her service games, can she do the same again here?

That felt like a potentially pivotal moment in this match.

Roberto Carballes Baena saves five break points to hold serve in the first game of the deciding set after 11 minutes of back-and-forth tennis.

Over to you, Jan Choinski...

Image source, Reuters

Coco Gauff is having more success on Varvara Gracheva's serve than her own.

A piercing cross-court backhand winner opens up a 0-30 lead for the third seed. Another long hit from Gracheva hands her opponent two break points.

A better first serve helps Coco Gauff to bring us to deuce, and a fiery forehand hands her advantage.

Varvara Gracheva sends a forehand long and Gauff gets the hold. This hasn't been easy for the American so far.

That's one way to redeem yourself. After a double fault, Coco Gauff flings down an epic ace.

But there's another one of those dreaded double faults and it's break point Varvara Gracheva.

Varvara Gracheva manages to hold off Coco Gauff this time around, forcing the American into two errors to wrap up her service game and keep herself within touching distance in this first set.

Image source, Getty Images

• On Louis Armstrong, American 12th seed Taylor Fritz is a set and a break to the good against Argentina's Camilo Ugo Carabelli.
• Former Grand Slam finalists Casper Ruud and Matteo Berrettini are on the brink of victories in their first-round matches.
• Spanish 26th seed Paula Badosa has won the first set 6-0 in 26 minutes against Switzerland's Viktorija Golubic.

Click on the link at the top of this page to view latest scores, results and the rest of today's schedule.

Roberto Carballes Baena is back on court but he seems to be having some trouble with his shoelaces now.

Shoelaces count as 'equipment failure' according to the Sky commentary team, so the Spaniard gets extra time to sort them out.

After a lengthy break, we're back under way at Flushing Meadows.

Another narrow escape for Coco Gauff. She gets the hold to back up her early break.

Varvara Gracheva misses the first break point, but she deals brilliantly with an overhead to bring up another one.

Not the best time to double fault, Coco. Break point Varvara Gracheva.

Big hitting from Varvara Gracheva. After a double fault from Coco Gauff, the French player fires a series of forehands, eventually forcing Gauff to concede.

However, the defending champion gets the next point after rushing to the net.

We go to deuce, though. A wild backhand from Gauff fizzes beyond the baseline.

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

Image source, Getty Images

Just incredible, two sets to love down.

How has Jan Choinski turned this match around? He was literally down and out in this match.

We are heading into a fifth set, almost four hours on the clock already.

18 winners from Choinski. He is playing with risk and it is paying off. He is going to have to keep being brave in this fifth set.

Roberto Carballes Baena pops off court. Probably to calm down more than anything else.

The Spaniard looks flustered as he heads to the nearest portaloo.

Jan Choinski, meanwhile, remains in his seat and uses the air con blower to keep cool.

Now it's Coco Gauff's turn. Varvara Gracheva double faults and the American has two break points.

And she gets it first time as Gracheva misses a backhand. After an iffy start, Gauff is finding her feet.

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.

Would you believe it, we're going to a decider.

Jan Choinski smashes his first set point into the net with a forehand but takes it at the second opportunity as he forces Roberto Carballes Baena wide of the court with another forehand.

From two sets and a break down to all square.

Can Choinski complete one of the great comebacks from here?

A sigh of relief from Coco Gauff, who manages to get out of that service game unscathed. Just about.

Varvara Gracheva is piling on the pressure early doors against the reigning champion.

Groans from the crowd in Arthur Ashe Stadium.

Varvara Gracheva has a third break point as Coco Gauff nets again.

Shot of the match from Jan Choinski and what a time to do it as he whips a forehand winner across court and past Roberto Carballes Baena.

A backhand winner then earns two set points!