Kei Nishikori faces a race against time to be fit for the US Open after revealing he has tested positive for Covid-19.

The 30-year-old Japanese announced on Sunday that he was self-isolating in Florida and as a result had pulled out of the Western and Southern Open, which has been moved to New York from its traditional venue in Cincinnati to act as a warm-up event for the Grand Slam tournament.

In a statement on his official app, Nishikori said: "Hi everyone, I have some unfortunate news today. This morning while still in Florida, I got tested for Covid19 and tested positive. I will have to pull out of the Cincinnati tournament at this time.

"Me and my team will get tested again on Friday, at which point I will have another update. I am feeling well and have very little symptoms, but will obviously be in complete isolation for the safety of everyone.

"We were planning to fly to New York tomorrow, but will obviously now stay in Florida. Next update will be on Friday."

Nishikori, currently ranked 31 in the world, has not played a competitive match since undergoing elbow surgery in October last year, although the ongoing pandemic has meant he has missed less tennis than he might ordinarily have done.

The US Open is due to get underway at Flushing Meadows on August 31.