Former world number one Maria Sharapova has revealed she failed a drugs test at the Australian Open.
The Russian, 28, tested positive for meldonium, a substance she has been taking since 2006 for health issues.
Sharapova, a five-time Grand Slam champion, said she was not yet aware of the sanctions she will face.
“I did fail the test and take full responsibility for it,” said Sharapova, who won the Wimbledon title as a 17-year-old in 2004.
“For the past 10 years I have been taking a medicine called mildronate by my doctor, my family doctor, and a few days ago after I received the letter from the ITF [International Tennis Federation] I found out it also has another name of meldonium, which I did not know.
“It is very important for you to understand that for 10 years this medicine was not on Wada’s [World Anti-Doping Agency] banned list and I had been legally taking that medicine for the past 10 years.
“But on 1 January the rules had changed and meldonium became a prohibited substance, which I had not known.”
She added: “I received an email on 22 December from WADA about the changes happening to the banned list and you can see prohibited items, and I didn’t click on that link.”
Sharapova has been the highest-earning female athlete in the world for the past 11 years, according to the Forbes list.
She first reached world number one in August 2005 and is currently seventh in the rankings – but she has played just four tournaments since Wimbledon last July as she struggled with an arm injury.
Her most recent match was a defeat by Serena Williams at the Australian Open in January, but Sharapova, who turns 29 in April, hopes to be able to return to tennis in the future.
“I made a huge mistake,” she said.
“I have let my fans down, and let the sport down that I have been playing since the age of four that I love so deeply.
“I know that with this I face consequences and I don’t want to end my career this way. I really hope to be given another chance to play this game.”
There had been speculation Sharapova was going to announce her retirement and a large media contingent gathered for the Los Angeles news conference, which was streamed live online.
“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.