New York, Sep 3 : Last year's finalist Ons Jabeur of Tunisia needed nearly three hours to post a 5-7, 7-6(5), 6-3 comeback win over Czech player Marie Bouzkova at Arthur Ashe Stadium. Saturday's win was the second straight three-set triumph for the 29-year-old from Tunisia. After her latest closely-contested win, Jabeur meets Zheng Qinwen, the rising 20-year-old from China, in the Round of 16 on Monday. Down 3-5, Jabeur had 15 errors to her opponent's five, and looked as if she was on her way to conceding the set. The Tunisian rallied, but Bouzkova took the first frame, 7-5. In the second set, the 29-year-old Tunisian was up a break at 5-4, when a physically ailing Bouzkova limped to her chair. After an off-court medical timeout, the Czech player returned with a look of distress on her face. Stumbling at times, and not even trying to retrieve Jabeur's drop shots, Bouzkova leveled the set when a wild Jabeur forehand sailed out, and went on to hold for a 6-5 lead. Jabeur, however, held again and forced a tiebreaker by taking the set 7-6(5). In the tiebreaker Jabeur broke Bouzkova -- at love -- to take a 2-0 lead. Naturally, Bouzkova broke right back and held to make it 2-2. Two games later, Bouzkova led 40-0, but the Czech lost five straight points, and Jabeur took a decisive 4-2 lead which she would not relinquish. In other action, reigning Wimbledon champion Marketa Vondrousova of Czech Republic needed only 56 minutes to claim a spot in the Round of 16, dispatching No.22 seed Russian Ekaterina Alexandrova 6-2, 6-1 on Saturday. With the win, Vondrousova matches her career-best showing at the US Open -- a run to the Round of 16 as a 19-year-old in 2018. In the Round of 16, Vondrousova will face American Peyton Stearns, which should bring back 2023 Wimbledon memories for both of them. In their lone prior meeting, Vondrousova beat Stearns in the opening round of the Czech's title run in London. Playing in just her fourth career Grand Slam main draw, 59th-ranked Stearns booked a spot in her first-ever second week at a major with a 6-4, 6-3 victory over Great Britain's Katie Boulter, ranked two spots lower at No.61. On the other hand, the No.3 seed American Jessica Pegula advanced to the fourth round in singles with a 6-4, 4-6, 6-2 victory over No.26 Ukrainian Elina Svitolina and set an all-American clash with her friend Madison Keys on Monday. With a win on Monday, Pegula will have reached the quarterfinals of three of the four majors for the second consecutive year. She won the only previous match against Keys -- a finalist here in 2017 and a semifinalist in 2018 -- last year in San Diego. /IANS