World number 29 Dayana Yastremska says she is in "shock" after a provisional ban for failing a doping test.
The 20-year-old Ukrainian said she was told by the International Tennis Federation (ITF) she had tested positive for mesterolone metabolite, an anabolic agent, in an out-of-competition test in November.
"I firmly state that I have never used any performance enhancing drugs or any prohibited substances," she said.
Yastremska has won three WTA titles.
"Yastremska had [and retains] the right to apply to the Chair of the Independent Tribunal convened to hear her case why the Provisional Suspension should not be imposed, but has chosen not to exercise that right to date," the ITF said in a statement.