Italian Health Minister Roberto Speranza said on Friday people who have been in Romania and Bulgaria in the past 14 days will be quarantined upon arrival in Italy, a move aimed at preventing the importation of COVID-19 cases.

"We found out with great bitterness the decision of the world number two to cancel her participation," the tournament's director Oliviero Palma said in a statement.

Palermo will be the first professional tennis event across the WTA and men's ATP Tours after a five-month break, with action scheduled to get underway on the clay courts of the Sicilian capital from August 3.

"Given the recent rise in Covid-19 cases in Romania and my anxieties around international air travel at this time, I have made the tough decision to withdraw from Palermo," Halep said on Twitter.

"I want to thank the tournament director and the Italian ministry of health for all their efforts on my behalf and I wish the tournament a successful week."

Halep, the reigning Wimbledon champion and 2018 French Open winner, has also committed to the Prague Open, scheduled to start on August 10.

Italy was the first European country to be hit hard by coronavirus but the amount of daily new infections being reported is a fraction of the numbers in late March. The country has recorded over 35,000 deaths from the virus.

Palma said the organisers had written an urgent letter to Italy's health minister, asking for exemption for tennis players taking part in the event.

"Yesterday we were optimistic, and we had informed Halep's staff about the fact that professional players are not obliged to quarantine," Palma said.

"We are embittered and profoundly disappointed."

Palermo will have strict health precautions and all players will undergo COVID-19 tests before they come, on arrival and every four days subsequently.

Australian Associated Press