Maria Sharapova has been banned for two years by the International Tennis Federation after failing a drugs test.
The Russian was provisionally banned in March after testing positive for meldonium at January’s Australian Open.
The heart disease drug, which 29-year-old Sharapova says she has been taking since 2006 for health issues, became a banned substance on 1 January 2016.
Sharapova will appeal against the ban, which is backdated to 26 January 2016, at the Court of Arbitration for Sport.
“I cannot accept an unfairly harsh two-year suspension,” she wrote on Facebook.
“With their decision of a two-year suspension, the ITF tribunal unanimously concluded that what I did was not intentional.
“The ITF asked the tribunal to suspend me for four years – the required suspension for an intentional violation – and the tribunal rejected the ITF’s position.
“I intend to stand for what I believe is right and that’s why I will fight to be back on the tennis court as soon as possible.”
The World Anti-Doping Agency admitted in April that scientists were unsure how long meldonium stayed in the system, and suggested athletes who tested positive before 1 March could avoid bans, provided they had stopped taking it before 1 January.
However, Sharapova had already admitted she continued taking the substance past that date, saying she was unaware it had been added to the banned list as she knew it by another name – mildronate.