In this Sept 5, 2019, file photo, Elina Svitolina, of Ukraine, returns a shot to Serena Williams during the semifinals of the US Open tennis championships in New York. Two more top-10 women -- Elina Svitolina and Kiki Bertens -- will miss the US Open, joining No 1-ranked Ash Barty in skipping the Grand Slam tennis tournament during the coronavirus pandemic. Svitolina posted, Aug 7, 2020, on social media that she doesn’t “feel comfortable to travel to US without putting my team and myself at high risk.”(ADAM HUNGER / AP)

Women’s world number five Elina Svitolina and Kiki Bertens, ranked seventh, on Friday joined a growing list of players withdrawing from this month’s US Open due to the COVID-19 pandemic.

Men’s defending champion Rafa Nadal and women’s world number one Ashleigh Barty have opted against travelling to New York to play the hardcourt Grand Slam as well as the Western & Southern Open that will work as a warmup for the US Open.

The United States has close to 5 million cases of COVID-19 and almost 160,000 people have died, according to a Reuters tally

“I understand and respect all the efforts they are putting to make it happen in a safe environment, but I still don’t feel comfortable to travel to US without putting my team and myself at high risk,” Ukrainian Svitolina, who reached last year’s semi-finals in New York, said on Twitter.

The United States has close to 5 million cases of COVID-19 and almost 160,000 people have died, according to a Reuters tally.

“The situation around COVID-19 is still worrying and the health of everyone and the control over this virus is priority,” said the 28-year-old Bertens on Instagram.

In this Aug 31, 2019, file photo, Kiki Bertens, of the Netherlands, returns a shot to Julia Goerges, of Germany, during round three of the US Open tennis championships in New York. (SARAH STIER / AP)

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The US Open organisers (USTA) are creating a bio-secure ‘bubble’ in New York to hold the tournament from Aug 31 without spectators. But concerns remain about whether players would face mandatory quarantines upon returning home from the US Open.

Former world number one Andy Murray, who won the US Open in 2012, said on Monday that players travelling to New York needed assurance that they would not face mandatory quarantines after returning to Europe.

“Our prime minister indicated yesterday that we should be quarantined for 14 days after coming back from the States,” Bertens said.

“Of course we respect this as a team and this would disturb our preparation for my beloved clay court tournaments in Rome and Paris.”

READ MORE: Murray wants assurance on quarantine issues before US Open

The Italian Open is scheduled to be held in Rome from Sept. 20 ahead of the French Open Grand Slam in Paris a week later.