NEW YORK (Reuters) - Greek Maria Sakkari emerged triumphant from a gruelling three hour, 30 minute battle with former champion Bianca Andreescu at the U.S. Open on Monday, clinching a 6-7(2) 7-6(6) 6-3 victory to reach the quarter-finals.

The contest on Arthur Ashe Stadium ended at 2:13 a.m. -- the latest finish to a women's singles match at the hardcourt major, which will crown a new women's champion following the Canadian's defeat.

"I actually think I have a very bad record with night matches," Sakkari told reporters.

"When I found out yesterday I'm playing night, I was not happy at all because I'm an early morning person. I still haven't figured out how I have to plan my day.

"Now, well, I can say that it happened, that I played tennis at 2:30 in the morning."

It was the first defeat at Flushing Meadows for 2019 champion Andreescu, who suffered an injury in the middle of the deciding set but kept fighting.

Sakkari helped the Canadian to an early break in the first set with a trio of double faults before finding her footing.

Andreescu, the 2019 champion, won a punishing 21-shot rally to open the first-set tiebreak before clinching the set with three straight points, capping it off with an ace.

Sakkari, who faces fourth seed Karolina Pliskova in the quarter-final, said she knew she had to change her approach to stay in the match.

"I knew that I lost the first set because I was doing some things wrong. I was not very brave. So I had to change that," she said.

The Greek struggled with her serve again in the second set, putting up five double faults, but broke her opponent in the second game to get her nose in front. She then held serve in an 11th game that lasted 10 minutes.

The second set tiebreak went Sakkari's way, the 17th seed clinching it at the fourth attempt.

Down 3-2 in the third set, Andreescu received treatment on her left thigh before leaving the court for a medical timeout and returning with her leg wrapped.

With Sakkari leading 5-3 and up 30-0 in the ninth game, a hurting Andreescu screamed, "This sucks!" but managed to fend off three match points before the Greek converted on a fourth.

Andreescu missed the 2020 season due to injury and the challenges of playing in the COVID-19 pandemic and failed to get beyond the first round at Wimbledon or Roland Garros this year.

Sakkari said she was prepared for the match to go even deeper but was happy it did not.

"I was prepared for 7-6 in the third. But if you know, if it comes easier then I'll take it," she added.

"I knew it was gonna be a very tough match. She loves this court, her best memories," said Sakkari, who reached the Roland Garros semi-finals earlier this year.

(Reporting by Amy Tennery in New York, additional reporting by Sudipto Ganguly and Steve Keating; Editing by Peter Rutherford)