Coco Gauff overcame a tough test from Zeynep Sonmez to book her place in the second round of the US Open with a straight-sets win.

Gauff showed her improvements on serve, particularly in the second set, as she dug in to earn a 6-3 6-4 win over Sonmez in 80 minutes.

The American started strongly with a hold to love and got her advantage in the seventh game of the first set with the first break.

That three-game winning streak put her in control before she saw out the set at the first attempt.

Gauff then opened the second set with a break, only to be pegged back at 2-2 as Sonmez stepped up the intensity.

The 22-year-old then saved three break points in a six-deuce, nine-minute sixth game in the set, but she claimed a big hold to take control of the match.

It started a three-game winning streak, and though she missed a match point after that, she made no mistake on her second as she rounded off the match with a love-hold.

"I don't know what put my mind at ease," Gauff said in her post-match press conference.

"I think maybe the confidence I had this week and knowing the opponent would have to play a really high level and me a really low level for it to not go my way.

"But Zeynep brought that high level today. I was just happy to get out of that second set."

Poetry in motion @CocoGauff kicks off her campaign under the lights of Arthur Ashe Stadium.#USOpen pic.twitter.com/dmB2hy0ShH

— wta (@WTA) September 2, 2026

Alexandra Eala is also through at Flushing Meadows, reaching the second round for the second consecutive year.

She earned a convincing 6-1 6-2 victory over Mary Stoiana in one hour and 17 minutes, earning her ninth win on hard court since Wimbledon.

There was an early exit for Belinda Bencic, though, as Yulia Putintseva came from behind to win 4-6 7-5 6-3 in just under three hours.

Gauff puts serving struggles behind her

Gauff spoke at length ahead of the US Open about the work she has done to improve her serve, and that was on show on Arthur Ashe Stadium.

She has now won 67 of her 71 completed grand slam matches after winning the opening set, and is undefeated in such matches at the US Open, with her record at 15-0.

Gauff hit five aces, and won 71% of her first serve points (29/41) as well as 64% on second serve (16/25).

The world number four has a strong record at the US Open as she looks to win the major for the second time.

She has won seven of her eight first-round matches in New York and has 81 grand slam match wins since the start of 2020. Only Iga Swiatek (109) and Aryna Sabalenka (106) have more.