Russian tennis star Maria Sharapova has announced she failed a drugs test at this year's Australian Open.
Sharapova, 28, said she took "full responsibility" for testing positive for meldonium, a substance she had been taking to treat "health issues" since 2006.
She has been provisionally suspended with effect from March 12 by the International Tennis Federation.
Speaking at a press conference in Los Angeles, the five-time Grand Slam champion said she was not aware that the medicine had been banned on January 1st 2016.
"I made a huge mistake; I let my fans down; I let the sport down that I've been playing since the age of four that I love so deeply," a visibly emotional Sharapova said.
She said she had been taking the medicine to help combat health issues including sickness, a magnesium deficiency, and signs of diabetes.
Sharapova also expressed hope that she would be given "another chance" to continue playing the game in future.
"I know that with this I face consequences and I don't want to end my career this way and I really hope that I will be given another chance to play this game," she said.
The Tennis Anti-Doping Programme (TADP) confirmed Ms Sharapova provided an anti-doping sample to them on January 26 2016 in association with her participation in the 2016 Australian Open.
The sample was analysed by a World Anti-Doping Agency (WADA) accredited laboratory, which returned a positive for meldonium, which is a prohibited substance under the WADA Code and, therefore also the TADP.
Ms Sharapova was charged on 2 March with an Anti-Doping Rule Violation.
TADP said Ms Sharapova had accepted the finding of meldonium in her sample.
There had been speculation that Sharapova was going to announce her retirement at the press conference.
"I know many of you thought that I would be retiring today but if I was ever going to announce my retirement it would not be in a downtown Los Angeles hotel with this fairly ugly carpet," she said.
The Russian became a global tennis star after winning Wimbledon as a 17-year-old in 2004.
She has played in only one tournament this year, losing to Serena Williams in the quarter-finals of the Australian Open.