World number one Iga Swiatek was made to work hard to beat lucky loser Kamilla Rakhimova in the US Open first round.

Poland's Swiatek was not at her best in a 6-4 7-6 (8-6) victory that took just under two hours on Arthur Ashe Stadium.

Swiatek, champion in New York in 2022, made her trademark quick start, racing out to a 4-0 first-set lead, but Rakhimova rescued a break before Swiatek served it out.

The top seed went up an early break in the second set but her frustration was evident when she swiped angrily at a ball after a long forehand gave the break back.

Rahkimova, who lost in the final round of qualifying, kept in touch with Swiatek and had three set points in the tie-break to force a decider.

However, Swiatek upped her aggression when it mattered to secure victory and set up a second-round meeting with Japan's Ena Shibahara.

Five-time Grand Slam champion Swiatek won her third successive French Open title in June and secured an emotional Olympic bronze medal last month.

However, she has only gone beyond the fourth round once in six appearances in New York - and that was when she won the title two years ago.

"At the beginning [it was] good but then I got a little bit tight and my opponent used that, so I was trying to get back to my game," Swiatek said.

"I'm pretty sure that day by day I'm going to get more rhythm."