Australian youngster Thanasi Kokkinakis will miss this month's US Open after pulling his pectoral muscle.

It is the latest in a wretched run of injuries for the 20-year-old, who has missed the majority of the year following shoulder surgery.

Kokkinakis suffered the injury when he returned to the practice courts after recovering from a stomach bug following the Rio Olympics.

"He finally got back on court after the stomach bug, he practised two hours in the morning, and then the second hit he was hitting some high forehands and he kind of felt it just a little bit. It's worse than a strain, so it's going to take a couple of weeks, probably, of not hitting, for that to heal," his agent, Rick Montz, told the Brisbane Times.

"He's probably going to go home for a couple of weeks and then come back and train [in Saddlebrook, Florida] for a while, play the last US Challengers and get a good three or four tournaments in before he goes home again to train for the Aussie summer. So it's frustrating; two steps forward, one step back, is the best way I can describe it."