New York, Sep 7 (IANS): American tennis player CoCo Vandeweghe reached the US Open semifinals, knocking out World No.1 Karolina Pliskova in straight sets.

The 20th seed Vandeweghe took an emphatic 7-6 (4), 6-3 win against the Czech Republic's Pliskova on Wednesday, who will hand the number one spot to Wimbledon champion Garbine Muguruza after staying just eight weeks on the top of the rankings, reports Xinhua news agency. 

Vandeweghe's victory means that the US Open will possibly have an all-American semifinal lineup for the first time since 1981 if Madison Keys can overcome Estonia's Kaia Kanepi later on Wednesday. American veteran Venus Williams and Sloane Stephens have already set up an all-American semifinal in the bottom half in the previous day.

"I won the juniors here when I was 16 and dreamed of playing on the real stage," said 25-year-old Vandeweghe.

Pliskova, who had to save a match point to beat China's Zhang Shuai in the second round, needed to fight back from breaks down in both sets to keep her challenge alive.

But Vandeweghe can pull away with her powerful groundstrokes every time the Czech posed a threat. Vandeweghe hit 24 winners compared to just 15 from Pliskova. The American also powered five aces on the way to her impressive victory.