The women's singles semi-finalists have been confirmed at the US Open tennis championship in New York with the last two quarter-finals decided.
Romanian second seed Simona Halep advanced to her first US Open semi-final by defeating two-time Australian Open champion Victoria Azarenka of Belarus 6-3 4-6 6-4.
Halep said it was a tough match, and at this level it was normal to play three sets.
She said she didn't know where she found the power to win but the public was amazing.
Halep advanced to a semi-final against Italy's 26th-ranked Flavia Pennetta, who upset Czech fifth seed Petra Kvitova, a two-time Wimbledon winner 4-6 6-4 6-2 in another quarter-final at Arthur Ashe Stadium.
Pennetta has a 3-1 career edge in matches against Halep.
Italian veteran Pennetta reached the New York semi-finals for the second time in three years, outsmarting fifth seed Kvitova to add to the Czech's Flushing Meadows frustration.
The Italian flag will feature prominently in the semi-finals with the 33-year-old Pennetta joined in the last four by 32-year-old compatriot Roberta Vinci, who booked her spot Wednesday with a victory over Frenchwoman Kristina Mladenovic.
Pennetta has always been at home on the New York hardcourts, having now advanced to quarter-finals or beyond in six of her last seven visits to the National Tennis Center.
The same courts, however, have not been kind to Kvitova, the two-time Wimbledon champion, who never ventured past the fourth round until this year.
Kvitova, one only two players to beat Serena Williams this season, had been in superb form, winning her final US Open tune-up in New Haven, and she carried that momentum into Flushing Meadows, reaching the quarter-finals without dropping a set.
World No.1 Serena Williams, who holds all four major titles and seeks a calendar Grand Slam, will face Italy's 43rd-ranked Vinci in the other semi-final.
Williams is chasing the first calendar Grand Slam since Steffi Graf in 1988 and trying to match Graf's Open Era career record of 22 Slam singles titles, two shy of Margaret Court's all-time record.