World number one Jannik Sinner has pulled out of the Cincinnati Open with a right knee injury, tournament organisers said on Sunday, handing the Italian a blow in his preparations for this month's US Open.

The 24-year-old Italian, who claimed his fifth Grand Slam title at Wimbledon last month, had also pulled out of the Canadian Open, a key warm-up event for the U.S. Open.

Sinner won the Cincinnati title in 2024 and finished runner-up to seven-times Grand Slam champion Carlos Alcaraz there last year.​‌

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

"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.

"I'm very disappointed not to be able to play in Cincinnati... I can't wait to be back next year and I'm now focusing on getting ready for the U.S. Open."

Sinner's withdrawal further depletes the field in Cincinnati, with U.S. Open champion Alcaraz also sidelined by a wrist injury.

The Cincinnati Open main draw begins on August 13, while the U.S. Open main draw gets underway on August 30.