Men's World No. 1 Jannik Sinner has pulled out of the Cincinnati Open due to a right knee injury, the Italian announced Sunday.

"After consulting with my doctors and my team, I have to announce that I need to withdraw from the Masters 1000 tournament in Cincinnati," he said in a statement posted on the ATP website.

"My right knee has been bothering me and even though we have been working hard with my medical team, I have to accept that I'm not ready to compete yet."

The tournament begins on Thursday, the same day as the end of the Masters event in Montreal, which Sinner also missed.

The five-time Grand Slam winner had been on a six-tournament winning streak at 1000 level heading into the North American hard-court swing, before skipping the event in Canada.

The 24-year-old said at the time the decision was taken to "prioritize my health."

Sinner's subsequent withdrawal from Cincinnati follows that of world No. 2 Carlos Alcaraz as he continues to battle a wrist injury.

The Cincinnati Open and Montreal Masters are the two principal warm-up events ahead of the final Grand Slam of the season, the U.S. Open, which starts in New York on Aug. 30.

Sinner has not played since successfully defending his title at Wimbledon last month, whereas Alcaraz has been out of action since withdrawing from the Barcelona Open in mid-April.

The pair disputed the U.S. Open final last year, with the 23-year-old Spaniard emerging triumphant in four sets.