The tournament is set to begin in New York City at the end of this month, but several players have misgivings over air travel and playing in the United States given the global health crisis.

Ukraine's Svitolinia is the world number five and Bertens of The Netherlands is ranked number seven.

Svitolina said in a statement tat she dd not feel "comfortable to travel to the US without putting my team and myself at high risk".

Bertens called the coronavirus situation in then US "worrying" and cited the need for a 14-day quarantine period upon returning to The Netherlands as a factor in her decision to skip the second Grand Slam of the year and instead focus on the upcoming clay-court season, which is due to include the French Open.

With women's world number one Ashleigh Barty having already withdrawn from the US Open, at least three of the women's top 10 will be absent.

World number two Simona Halep - a two-time Grand Slam champion - has suggested she will opt against playing, but was included on the initial entry list as were Svitolina and Bertens.

The provisional women's field includes 13 past Grand Slam champions.

Rafael Nadal, Stan Wawrinka, Nick Kyrgios and Gaël Monfils are among the high-profile men's players who will not be in action at Flushing Meadows, while Roger Federer is injured.

Although COVID-19 cases are well down from what they once were in New York, the US has had more than 40,000 new cases each day for more than a month.

The US death toll - more than 162,000 - is the largest in the world.

In excess of 32,000 people have died as a result of the pandemic in the state of New York.

The Billie Jean King National Tennis Center - the US Open venue - was even turned into a makeshift hospital at one point.