New York: World No. 1 Simona Halep was swept aside 6-2, 6-4 by 44th-ranked Kaia Kanepi on Monday, the first top-seeded woman ever to lose in the US Open first round.

It was a second straight first-round exit at Flushing Meadows for Romanian Halep, who dropped her opening match to Maria Sharapova last year.

The French Open champion had no answer for Kanepi's powerful groundstrokes. The Estonian fired 26 winners to Halep's nine and even her 28 unforced errors didn't threaten to derail her challenge as she brought the rallies to quick ends and remorselessly punished Halep's second serve.

"Yesterday I thought I have beaten the world number one just once, today I had another chance," said a beaming Kanepi, who defeated then No. 1 Caroline Wozniacki in Tokyo back in 2011.

Kanepi, whose six Grand Slam quarter-final appearances include a run to the last eight in New York last year, earned a second-round meeting with Swiss qualifier Jil Teichmann, a 6-3, 6-0 winner over Dalila Jakupovic.

In men's singles, former champion Stan Wawrinka defeated Grigor Dimitrov for the second successive Grand Slam, knocking the eighth-seeded Bulgarian out in the very first round.

Wawrinka, the 2016 winner who missed last year's tournament as he underwent two knee surgeries, swept to a 6-3, 6-2, 7-5 victory at the Arthur Ashe Stadium to repeat his opening round triumph over Dimitrov at Wimbledon.

"The last time I played on this great court, I won the title. So, it was great to be able to come back and play again," said the 33-year-old Swiss.

"The level was really high, there were lots of emotions out there. It's always tough to play your best in the first round."

Wawrinka, the former world number three, now down at 101, shrugged off having to take a medical time-out early in the third set. "It was very humid and I felt something.

"I am just coming back from injury, so you never know how your body will react."

Andy Murray, on his return to the Grand Slam stage, suffered an initial hiccup against 448th-ranked Australian James Duckworth but went on to wrap up the match in four sets. The Scotsman lost the first set 6-7(5), but played smart and compact tennis to win the next three 6-3, 7-5, 6-3.

Seventh seed Elina Svitolina also powered into the second round, thanks to a 6-3, 1-6, 6-1 victory over Sachia Vickery.

Elina made a slow start to the match but powered through to take the opening set. She suffered a major wobble in the second, which was dominated by her opponent, but raised her game in the third and final set to claim the win in little over an hour-and-a-half.

Vickery came out firing and claimed the opening game against serve, but after holding hers, the set swung violently in the favour of her opponent, who won five successive games.

The American had adopted an aggressive approach and threatened to get back on terms in the ninth game, in which she earned two break points with some smart hitting. However, the world No.78 was unable to complete the comeback and saw the opening set elude her when she fired a forehand long.

Again, it was the 23-year-old who made the running at the beginning of the second. She was gifted a break point when the Ukrainian made a double fault, and some stubborn defence when given that chance saw Elina net an overhead.

That unforced error typified the second set for the higher-ranked player. Mistakes became commonplace, and while some of these were forced by the persistence of her rival, they were both more numerous and easier forced than Elina would have wished.

The second set alone yielded 11 unforced errors and just one winner.

By contrast, Vickery was playing with controlled aggression and when a deft drop shot brought up the chance for another break, it was handed to her as Elina again netted.

Agencies