Maria Sharapova has announced she will launch an immediate appeal to the Court of Arbitration for Sport (CAS) after being suspended for two years.
Sharapova, a winner of singles titles at all four grand slams, was provisionally banned by the International Tennis Federation (ITF) in March after testing positive for meldonium at this year's Australian Open.
The Russian claimed to be unaware that meldonium had been added to WADA's prohibited list at the start of 2016.
Following a two-day hearing in May, the ITF announced on Wednesday that an independent tribunal had imposed a two-year suspension on Sharapova, backdated to January 26, 2016 - the date of her positive test in Melbourne.
Sharapova responded to the verdict almost immediately via her official Facebook page, arguing her ban was too severe.
"Today with their decision of a two-year suspension, the ITF tribunal unanimously concluded that what I did was not intentional," wrote the former world number one.
"The tribunal found that I did not seek treatment from my doctor for the purpose of obtaining a performance-enhancing substance. The ITF spent tremendous amounts of time and resources trying to prove I intentionally violated the anti-doping rules and the tribunal concluded I did not.
"You need to know that 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.
"While the tribunal concluded correctly that I did not intentionally violate the anti-doping rules, I cannot accept an unfairly harsh two-year suspension. The tribunal, whose members were selected by the ITF, agreed that I did not do anything intentionally wrong, yet they seek to keep me from playing tennis for two years.
"I will immediately appeal the suspension portion of this ruling to CAS, the Court of Arbitration for Sport.
"I have missed playing tennis and I have missed my amazing fans, who are the best and most loyal fans in the world.
"I have read your letters. I have read your social media posts and your love and support has gotten me through these tough days. 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."
A statement from WTA CEO Steve Simon read: "It is important at all times for all players to be aware of the rules and to follow them. In this case, Maria has taken responsibility for her mistake from the outset.
"The WTA supports the process that the ITF and Maria have followed. The ITF has made its ruling and, under the Tennis Anti-Doping Program, the decision may be appealed to the Court of Arbitration for Sport.
"The WTA will continue to follow this closely and we hope it will be resolved as soon as possible."