Del Potro, the 2009 champion from Argentina, has not played since slipping and hurting his knee on the grass in the Wimbledon tune-up at Queen's in June. He underwent surgery before returning home to begin his recovery.

"I'm very happy to tell you that I'll play in Stockholm and Vienna in October. These two tournaments are very special to me, as I had the chance to win both of them," Del Potro tweeted.

The injury-plagued 30-year-old was forced to miss this year's US Open after finishing runner-up to Novak Djokovic in the 2018 final.

He first fractured his kneecap last October when he fell during a match at the Shanghai Masters.

Del Potro is a two-time winner of the Stockholm Open, which runs from October 14 to 20, and also claimed the 2012 title in Vienna, where he plans to compete the following week.

Del Potro reached a career high of third in the world but is currently ranked 16th, although he will tumble down the standings after the US Open.