Nishikori has withdrawn from the Western and Southern Open – the US Open warm-up event that has been moved from Cincinnati to New York City because of the coronavirus pandemic – following his positive test.

The 2014 US Open runner-up and Olympic bronze medallist has not yet revealed his plans for the Grand Slam at Flushing Meadows, which begins on August 31.

His positive test came just 24 hours before he was due to leave his base in Florida for New York.

"Me and my team will get tested again on Friday (August 21), at which point I will have another update," Nishikori, the world number 31, said.

"I am feeling well and have very little symptoms but will obviously be in isolation for the safety of everyone."

Nishikori could become the latest player to pull out of the US Open amid the COVID-19 crisis.

Defending champion Bianca Andreescu is one of three of last year's women's semi-finalists to withdraw from the tournament, alongside current world number one Ashleigh Barty of Australia.

Romania's world number two Simona Halep has today also pulled out, with the two-time Grand Slam winner saying health was "at the heart" of her decision.

Men's world number one Novak Djokovic has committed to playing, but reigning champion Rafael Nadal will be absent.

Players competing at the US Open have to enter a "bio-secure bubble", including mandatory tests before being allowed into the Flushing Meadows site.

Djokovic is among the players to have criticised the COVID-19 safety measures that are set to be implemented at the event.

The US is the worst-hit country by COVID-19 in the world, recording more than 5.5 million cases and at least 173,000 deaths.