Former champion Juan Martin del Potro has withdrawn from the US Open as he continues his recovery from knee surgery.

Del Potro, 30, underwent successful surgery on a fractured right kneecap in June and the Argentinian will miss the year's final grand slam.

The 2009 champion and last year's runner-up at Flushing Meadows, Del Potro's career has been ruined by wrist injuries and the US Open marks the third major he will miss in 2019.

Del Potro, ranked 12th in the world, returned to the top 10 in the rankings in January 2018 after three and a half years.

The US Open has been Del Potro's best grand slam, where he holds a 35-9 win-loss record to go with his two finals appearances.

Denis Kudla moves into the main draw in New York, with Chris Eubanks receiving the wildcard initially given to his American compatriot.