Ons Jabeur kept her dream of a first Grand Slam alive at the US Open on Saturday, reaching the last 16 after finally overcoming injured opponent Marie Bouzkova in three sets.

Tunisian fifth seed Jabeur, whose own US Open campaign has been disrupted by a flu virus, completed a 5-7, 7-6 (7/5), 6-3 victory to subdue Bouzkova in 2hr 56min.

A contest of high drama on the Arthur Ashe Stadium saw Bouzkova play virtually half of the match on one leg after suffering a thigh injury midway through the second set.

The 25-year-old Czech 31st seed left the court for a lengthy medical timeout after clutching her thigh in pain.

She appeared to be close to tears when she returned, but somehow managed to battle bravely on despite severely limited mobility.

Bouzkova was often seen grimacing and wincing in pain whenever she needed to push off her injured leg, but remarkably continued to complete the match.

At one point she consulted her coaching staff in the stands and said simply: "I have to."

"Man it was a very tough match," Jabeur said afterwards. "We both played really well. She didn't want to stop. She's a great player.

"This is a tough sport. You always don't want to give up. I really respect her for that. I think we both had a great battle tonight, and hopefully I'll continue getting this 'warrior' symbol with me during this great tournament."

Jabeur admitted she had been incredulous at times as Bouzkova soldiered on despite her injury.

"When I saw her struggling with her leg I tried to make her move as much as I can," Jabeur said. "I know that's not nice but I was trying to win the match.

"At certain times I was like 'Is she really injured?' I wasn't sure."

Jabeur, who also needed three sets in round two after a difficult opening match earlier this week, once again found herself in trouble early on against Bouzkova.

But the injury changed the complexion of the match, even though the ailing Bouzkova took her to a tie-break in the second set.

Jabeur grabbed an early break in the final set, and then served for the match in the ninth game.

There was another twist as Bouzkova saved two match points after trailing 15-40, but Jabeur finally clinched victory on her third match point.

Jabeur, who will now face China's Zheng Qinwen in the last 16 on Monday, said her punishing training regimen in Tunisia had helped prepare her for the demands of the tournament.

"It was super hot in Tunisia, super humid," Jabeur said. "Honestly, I was fighting to just finish the practice. It would have been much easier to stop the practice, but we didn't.

"I was really fighting on those practices the same as during those matches."