Serena Williams passed her toughest test so far at the US Open to beat Karolina Pliskova and reach the semi-finals for a ninth consecutive time.
Williams, seeded 17th, won 6-4 6-3 against the Czech eighth seed.
The American, 36, is seeking her first Grand Slam trophy since giving birth to daughter Olympia last September.
If she wins it would be her 24th major title - equalling Australian Margaret Court's all-time record - and her seventh at Flushing Meadows.
Latvia's Anastasija Sevastova, who knocked out defending champion Sloane Stephens earlier on Tuesday, waits in the last four.