Elina Svitolina and Kiki Bertens, both ranked in the women's top 10, withdrew on Friday from the US Open, joining other senior players in pulling out because of concerns about coronavirus.
"Considering all aspects, I have decided not to play the US Open," Svitolina, a Ukrainian ranked number five, wrote on social media.
Bertens, a Dutchwoman ranked seventh, said on Instagram that she made her decision after a "long consideration."
"The situation around Covid-19 is still so worrying that the health of everyone comes first and control of this virus is obviously a priority," Bertens said.
Bertens said she was heeding Dutch government warnings while Svitolina said she did not want to risk travelling.
Svitolina thanked the US Tennis Association and WTA "for giving the players a chance to play."
"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 the US without putting my team and myself at risk," wrote Svitolina, a semi-finalist at the US Open last year.
Bertens announced her decision after the Dutch government tightened health measures on Thursday.
"Our prime minister also indicated yesterday that we should be quarantined for two weeks after coming back from the States," she said.
"This would hinder the preparation for my beloved clay court tournaments in Rome and Paris," Bertens said, indicating that she could play at the French Open, which is due to start in Paris on 27 September.
Svitolina and Bertens follow other top players who have announced their withdrawal from New York including Rafael Nadal and women's world number one Ashleigh Barty.
Serena Williams, Novak Djokovic and Andy Murray are all still due to play.