By EMILY SHAPIRO, ABC News(NEW YORK) — Tennis champion Novak Djokovic has issued an apology after he became the fourth player to test positive for COVID-19 at his charity tournament.Djokovic, who ranks No. 1 in the sport, said in a statement Tuesday, “I am so deeply sorry our tournament has caused harm.””Everything the organizers and I did the past month, we did with a pure heart and sincere intentions. We believed the tournament met all health protocols and the health of our region seemed in good condition to finally unite people for philanthropic reasons,” he said. “We were wrong and it was too soon. I can’t express enough how sorry I am for this and every case of infection.” Three tennis players competing at a tournament Djokovic organized in Croatia and Serbia have tested positive. All matches have been canceled. Djokovic, who ranks No. 1 in the sport, defended his tournament, saying it was “meant to unite and share a message of solidarity and compassion throughout the region.” “The Tour has been designed to help both established and up and coming tennis players from South-Eastern Europe to gain access to some competitive tennis while the various tours are on hold due to the COVID-19 situation,” Djokovic said in a statement. “It was all born with a philanthropic idea, to direct all raised funds towards people in need and it warmed my heart to see how everybody strongly responded to this.” “We organized the tournament at the moment when the virus has weakened, believing that the conditions for hosting the Tour had been met,” he said. “Unfortunately, this virus is still present, and it is a new reality that we are still learning to cope and live with.” Djokovic said he will self-isolate for the next 14 days and retake a coronavirus test in five days. Copyright © 2020, ABC Audio. All rights reserved.