NEW YORK, Sept 4 (Reuters) - Greek Maria Sakkari dismantledthe defences of twice Grand Slam champion Petra Kvitova to win 6-4 6-3 to reach the fourth round of the U.S. Open on Saturday. The 17th seed relied on her powerful serve once again, winning all but one of her first-serve points in the opening set and firing off nine aces in the match on Arthur Ashe Stadium. In the second set, her Czech opponent dropped serve in the first game but refused to go quietly, fending off seven break points - including two in the third game to hold - but could not match the power of Sakkari, who struck 13 winners in the set. "I think my serve was probably my biggest weapon today and of course playing in front of this crowd was unbelievable," said Sakkari, who lost to Serena Williams in a fourth-round, three-set thriller a year ago in front of empty stands. "It"s always tough to play against Petra, because she hits very hard, probably the hardest on the tour," she added. "I"m very pleased with the way I served, the way I returned, and my attitude on court." The Roland Garros semi-finalist next faces sixth-seededCanadian Bianca Andreescu, who is looking to recapture the magic of her successful 2019 U.S. Open after missing the 2020 season due to injury and the challenges of competing in the pandemic. "She can do everything on the court. She can hit hard, she can play high balls, can slice, can dropshot," said Sakkari. "She"s experienced because she has won big tournaments." Sakkari lost in their only previous meeting, a hard-fought, three-set semi-final in Miami in April. "Bianca is one of the toughest players to play on the tour, and I"m prepared that it"s going to be a very, very tough match for both of us," Sakkari said. "I"m just going to stick to what I"m doing good right now and stay with the same mindset."