It will be the number two seed Iga Swiatek who will serve first and get us under way in this one.

* denotes server

There it is. Marta Kostyuk can only skew her return wide and there's the break back for Katie Boulter.

A chance for an immediate response for Sonay Kartal as Beatriz Haddad Maia nets - 15-30 in favour of the Briton.

A double fault follows, gifting two break points to Kartal...

Haddad Maia saves the first with a great one-two punch behind a powerful first serve, but Kartal gets it done at the second attempt!

It's a long, long rally and Haddad Maia blinks first, sending a backhand from behind the baseline into the net.

Opportunity missed. Marta Kostyuk wipes out all three break points.

Katie Boulter had the court at her mercy on the third but just overhit her forehand wide.

Hang on though, Boulter will have a fourth chance.

Hello.

Serving problems seem to be catching. Marta Kostyuk's serve goes missing and two double faults allow Katie Boulter a chance at three break points.

A first break of serve of the match.

At 30-30, Beatriz Haddad Maia attacks the net and forces Sonay Kartal to go long on the backhand side.

The break point saved by the Briton, though - Kartal gets her first serve in and Haddad Maia is long with the return.

However, Kartal nets a forehand to give away another break-point chance and Haddad Maia's aggression pays off once more.

Katie Boulter just struggling a little on serve.

A double fault hands Marta Kostyuk a gift for 15-15. Then the Brit does it again for 15-30. Not ideal.

A powerful forehand down the line gets her back on track then Kostyuk sends back-to-back forehands wide to hand over the game.

Image source, Getty Images

First up on court in Arthur Ashe Stadium is world number two Iga Swiatek, who won the Cincinnati Open earlier this month and finished as a runner-up in the revamped mixed doubles tournament last week.

Swiatek will be hoping to win back-to-back Grand Slams, having picked up her sixth major at Wimbledon, but says "it doesn't make sense to call anyone the favourite" going into the tournament at Flushing Meadows.

Colombia's Emiliana Arango lies in wait on her US Open main-draw debut, having burst into the top 100 with a second-round finish at Roland Garros earlier this year.

If Swiatek comes through her opening match as anticipated, she will take on the Netherlands' Suzan Lamens or the United States' Valerie Glozman.

Nicely done from Marta Kostyuk. She drags Katie Boulter into the net and the Brit can only overhit her forehand.

A big serve which Boulter can only ping wide hands her the hold.

Kostyuk has only missed three first serves across her three service games.

Beatriz Haddad Maia gets to 40-0 on serve but an unforced error and a Sonay Kartal forehand winner give the Brazilian some work to do to hold.

She eventually does so with a backhand drop shot that gives Kartal no chance.

That's more like it from Katie Boulter and she stops the rot to take the hold to love.

Leon Smith
GB Davis Cup captain on BBC Radio 5 Sports Extra 2 and BBC Sounds

This has the potential to be a long match.

Both are very good athletes and very tenacious, got good hand skills and variety. Maia has been at the top of her game for quite a while and she's going try to expose the reach that Sonay has by opening up the court. She enjoys the athletic side of the game so I would try to bore her to death.

That looked like a really good passing shot down the line from Katie Boulter but it actually dropped millimetres wide of the paint.

A hold to love for Marta Kostyuk consolidates her break of serve.

Image source, Getty Images

Sonay Kartal is more than holding her own in the opening exchanges on Court 12 against Beatriz Haddad Maia, the 18th seed.

A couple of fine forehand winners take her to 40-0 and, although an overhead attempt is netted on the first game point, Kartal quickly wraps it up to level things in the first set once again.

Katie Boulter just struggling a little on serve and Marta Kostyuk stays patient to earn herself a break point.

Boulter can only nudge her forehand into the net and that hands over an early break of serve.

Beatriz Haddad Maia shows exceptional touch with a half-volley that drops just over the net for a winner. Sonay Kartal tries to chase it down but it's just too good.

That lefty serve out wide is a big weapon for the tall Brazilian, producing a second ace of the match to secure a hold to love.

Leon Smith
GB Davis Cup captain on BBC Radio 5 Sports Extra 2 and BBC Sounds

Marta Kostyuk is a tough opponent, who has had some really good and surprisingly poor moments this year, so she isn't in amazing rhythm either.

She is a very good and talented competitor, but in her last few tournaments she has withdrawn or retired from matches because of a wrist injury and something else in her arm.

There's something not quite right there so Katie Boulter needs to go into her deep competitor mode and work as hard as she can today.

Katie Boulter making life difficult for Marta Kostyuk in her opening service game as she twice takes her to deuce.

Boulter fires long, though, and that secures the hold for the Ukrainian.

Image source, Getty Images

There's a height difference of eight inches between Beatriz Haddad Maia (6ft) and Sonay Kartal (5ft 4in).

British number three Kartal falls 0-30 behind in her first service game on Court 12, but recovers with four straight points to get herself on the scoreboard.

Leon Smith
GB Davis Cup captain on BBC Radio 5 Sports Extra 2 and BBC Sounds

It has been a tricky year for Katie Boulter. A year ago she was at a career-high world ranking and she cemented herself at the Grand Slams, but it isn't always easy to back that up.

But when she does find her momentum, she is so dangerous. It is hot and sunny here, so the balls will be going quickly through the court, which is good news for her if she serves well today.