Two-time Grand Slam champion Simona Halep was slammed with a provisional suspension by the International Tennis Integrity Agency after failing a drug test during the US Open in August.
The ITIA announced the punishment on Friday for Halep who is currently No. 9 in the WTA rankings.
Former no.1 Halep won Wimbledon in 2019 and the French Open in the year 2018.
In a social media post, Halep called the news of her positive test "the biggest shock of my life," adding: "Facing such an unfair situation, I feel completely confused and betrayed."
"I will fight until the end to prove that I never knowingly took any prohibited substance," Halep wrote, "and I have faith that sooner or later, the truth will come out."
The ITIA said Halep tested positive in New York for the banned substance Roxadustat, a drug approved for medical use in the European Union to treat the symptoms of anemia caused by chronic kidney failure.
Halep said she was told her test showed "an extremely low quantity."
According to the EU's medicines agency, which approved Roxadustat last year, it stimulates the body to produce more of the natural hormone erythropoietin, or EPO, which has long been a doping product favored by cyclists and distance runners.
During a provisional suspension, a tennis player is ineligible to compete in, or attend, any sanctioned events.
Tennis authorities will handle Halep's case and any ruling can be challenged by the World Anti-Doping Agency in an appeal to the Court of Arbitration for Sport.
"Today begins the hardest match of my life: a fight for the truth," Halep wrote on Twitter.
(Inputs from PTI)