NEW YORK • Serena Williams broke through another barrier on Monday, her 308th Grand Slam match win taking her past Roger Federer for the most wins in Grand Slam tournaments and into the quarter-finals of the US Open.

"Wow, it's really exciting," said the American tennis star of moving out of a tie with Swiss great Federer. "This is where it all started, so it's always so magical out here for me - 308 sounds pretty good."

As Williams, never seriously challenged in a 6-2, 6-3 victory over 52nd-ranked Yaroslava Shvedova, sailed on, one of the two players with a chance to topple her from the world No. 1 spot bowed out.

Fourth-seeded Agnieszka Radwanska was shocked by 18-year-old Croatian Ana Konjuh 6-4, 6-4.

Second-seeded Angelique Kerber is the only player left with a chance to end Williams' 186-week reign atop the rankings. But the German can ill afford to lose to last year's finalist Roberta Vinci, the seventh seed from Italy. The result of their quarter-final yesterday was unavailable by press time .

Denmark's Caroline Wozniacki and Latvian Anastasija Sevastova will also battle for a semi-final berth this morning (Singapore time).

Kerber's run to the quarter-finals means Williams must at least reach the final to stay top for a 187th consecutive week, which would also be a record. If both Kerber and Williams make the final, the American will have to win to extend her reign.

Williams will tackle Simona Halep in the quarter-finals today, after the fifth-seeded Romanian's 6-2, 7-5 victory over Spain's Carla Suarez Navarro.

Despite injury fears sparked by the sore shoulder that hampered her at the Rio Olympics, Williams has barely been tested since arriving at Flushing Meadows, where she claimed the first of her six US Open titles in 1999.

She has reached the business end of the tournament without dropping a set or even her serve. She has faced just one break point in four matches.

A seventh US Open title would take her past the record she shares with Chris Evert, and would also break the Open era record of 22 Grand Slam crowns she shares with Steffi Graf.

Halep, beaten in seven of eight previous encounters with Williams, was already bracing herself for the challenge.

"She's like the best player in the world. I don't have to be afraid or to have emotions because I have nothing to lose," said the Romanian. "It's just a huge challenge for me."

The tantalising prospect of a semi-final clash between Williams and her sister Venus evaporated as the older Williams fell to hard-hitting Czech Karolina Pliskova 4-6, 6-4, 7-6 (7-3).

Venus was unable to convert her lone match point as Pliskova, serving at 5-4 in the third, saved herself with a forehand volley, then held to extend the match.

With another break under her belt Pliskova had a chance to close it out at 6-5, but, after surging to a 40-0 lead, she lost five straight points as Venus forced the decider.

"In the tie-breaker, I went for a little bit more, but I didn't put the ball in enough," said the 36-year-old American, whose seven Grand Slam titles include two US Opens. "I went for some aggressive shots, didn't necessarily put them in."

In her first Grand Slam quarter-final, Pliskova will take on Konjuh.

AGENCE FRANCE-PRESSE

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