MOSCOW - Romania's world number one Simona Halep on Tuesday withdrew from the Kremlin Cup, a joint WTA and ATP event, due to concerns over an ongoing back injury. "I tried everything I could to be ready here as I really wanted to play," Halep said. "But unfortunately the back is still causing me pain and I don't want to take any unnecessary risks." The 27-year-old's appearance in Moscow and the WTA Finals had been in doubt when she withdrew from Beijing two weeks ago and was diagnosed with a herniated disk in her back. Halep, who has already qualified for the WTA year-ending finals in Singapore, said she needed more time to recover completely from her back injury. "While it's disappointing to withdraw, I know it's important to put my health first," she added.