Two-time Grand Slam champion Simona Halep has been provisionally suspended from tennis after testing positive for a banned substance.
The former world number one provided a sample, which tested positive for roxadustat, at August’s US Open.
Roxadustat is an anti-anaemia drug which stimulates the production of red blood cells in the body.
Romanian Halep, now ranked ninth in the world, said the positive result came as the “biggest shock of her life”.
“Today begins the hardest match of my life: a fight for the truth,” the 31-year-old wrote on Twitter.
“Throughout my whole career, the idea of cheating never even crossed my mind once, as it is totally against all the values I have been educated with.
“Facing such an unfair situation, I feel completely confused and betrayed.”
Halep, who won the French Open in 2018 and Wimbledon the following year, said that she had tested positive for roxadustat “in an extremely low quantity”, adding she would “fight until the end”.
She is the highest-profile tennis player to fail a drugs test since Maria Sharapova in 2016.
She has won two titles on the WTA Tour this year, with her best Grand Slam result coming at Wimbledon, where she reached the semi-finals.