US Open 2016: Top seeds Serena Serena, Angelique Kerber on collision course

New York: Serena Williams and Angelique Kerber try to line up their third Grand Slam title clash of 2016 on Thursday, taking on opponents hungry for a first major win in the US Open semi-finals.

It was at the semi-final stage at Flushing Meadows last year that Williams crumbled under the pressure of chasing a rare calendar-year Grand Slam as she fell to eventual runner-up Roberta Vinci.

This year the stakes are different but still high. With Kerber in the last four, Williams must get past hard-hitting Czech Karolina Pliskova and into the final to retain her world number one ranking.

If Kerber beats former world number one Caroline Wozniacki on Thursday night to advance, Williams will have to beat her in the final to extend her current reign atop the rankings to a record-breaking 187 weeks.

Williams is also seeking a seventh US Open title and a 23rd Grand Slam singles title -- both of which would be Open era records.

After facing, and saving, just one break point in her first four matches, Williams overcame a stern quarter-final test from fifth-seeded Romanian Simona Halep on Wednesday to advance.

She kept her frustration in check as Halep fended off 12 break points in the second set, firing 18 aces to get through 6-2, 4-6, 6-3.

In Pliskova she`ll face a long-time top 20 player enjoying a Grand Slam breakthrough many observers feel is overdue. The Czech has finally made it past the third round of a major at the 18th time of asking.

Through her convincing quarter-final win over Croatian teenager Ana Konjuh, Pliskova has taken her WTA-leading 2016 tally of aces to 439.

That serve and the easy power of her groundstrokes carried Pliskova to the biggest title of her career in Cincinnati last month.

She upset Kerber in the final there -- thwarting the German in her first chance to seize the number one ranking -- but acknowledged that Williams will be another matter.

"Always there is a chance, so I`m going to do everything to get at least close to the final," Pliskova said.

"She`s a big hitter and she can have 50 winners and you cannot do much about it," added Pliskova, who ousted sixth-seeded Venus Williams in the fourth round before dismantling Konjuh 6-2, 6-2 in the quarters.

Serena said she expected to get a few tips on Pliskova from her sister, but having produced a tournament-leading 60 aces herself in Flushing Meadows she didn`t need Venus to tell her one thing: "There will be a lot of aces in that match."Kerber, who toppled Williams in the Australian Open final and fell to the American in the Wimbledon championship match, faces experienced Dane Wozniacki.

Twice the year-end number one, Wozniacki reached US Open finals in 2009 and 2014 and the semi-finals in 2010 and 2011, and she`s a vastly more dangerous opponent than her current world 74 ranking -- the product of an ankle injury that sidelined her for three months -- suggests.

"I always believe in myself no matter what my ranking," said Wozniacki after surging past a hobbled Anastasija Sevastova 6-0, 6-2 in the quarters. "I`ve beaten pretty much everyone in the draw before."

Kerber, meanwhile hs been on the fast track in 2016 and her newfound poise was on display in her quarter-final win over Vinci.

Three times Vinci went up a break in the first set and three times Kerber came back, finally gaining a decisive fourth break to take the set 7-5.

She produced just three unforced errors in winning the second set 6-0.

"I think I`ve grown a lot in the last few years," Kerber said. "I`m staying more positive and believing in my game. I think that right now I can win matches like that."

It`s a change from her first Grand Slam semi-final appearance, at the US Open in 2011 when she fell to eventual champion Samantha Stosur.

"For me, I`m going out on Arthur Ashe, on the stadium, and playing against top player, I have more confidence going out there," she said. "I know that I can beat everybody."