PERTH, Australia (AFP) — Coco Gauff pulled off double duty to drag defending champion United States into the United Cup semifinals on Wednesday while world No. 2 Iga Swiatek did her bit for Poland.

Fourth-ranked Gauff, who suffered a surprise defeat last time out, put the United States on their way in their quarterfinal against Greece with a 6-3, 6-2 win over former world No. 3 Maria Sakkari in Perth.

Stefanos Tsitsipas brought Greece level by defeating struggling Taylor Fritz 6-4, 7-5.

In the deciding mixed doubles, Gauff teamed up with Christian Harrison to battle past Tsitsipas and Sakkari 4-6, 6-4, 10-8.

The 21-year-old Gauff struggled with her serve as she suffered her first-ever defeat at the United Cup on Monday when she was stunned by Spain’s Jessica Bouzas Maneiro. 

“Definitely a much better match today,” Gauff said after making light work of Sakkari.

“Last match, I just tried to erase it. That’s the beauty of this tournament.”

“So definitely happy to give my team the lead today.”

Six-time Grand Slam champion Swiatek beat 97th-ranked Suzan Lamens 6-3, 6-2 in the tie against the Netherlands in Sydney.

Hubert Hurkacz, on his way back after being out for seven months following knee surgery, defeated Tallon Griekspoor 6-3, 7-6 (7/4) as Poland sealed their Last-Eight spot.

Poland will play hosts Australia, with the winner facing the United States for a place in Sunday’s final.

The mixed-team United Cup features 18 teams and serves as build-up towards the Australian Open, which starts on 18 January.