Serena Williams' bid to reach the US Open final was put on hold as the women's semi-finals were rescheduled due to rain.
The forecast predicted rain at Flushing Meadows throughout Thursday evening and both matches will now be on Friday, with play starting at 4pm (BST).
The men’s semi-finals, also scheduled for Friday, will begin at 10pm.
Williams takes on unseeded Italian Roberta Vinci and number two seed Simona Halep plays another Italian Flavia Pennetta.
In the men's draw, Novak Djokovic faces defending champion Marin Cilic while Roger Federer is up against fellow Swiss Stan Wawrinka.
Serena beat her sister Venus 6-2 1-6 6-3 to reach the semi-finals and now stands two victories away from becoming the first player to hold all four major titles in a year since Steffi Graf in 1988.