Amir Khan expects to find out later today if his world light-welterweight title fight against American Lamont Peterson will go ahead as scheduled.
Peterson tested positive for a banned steroid and the Nevada State Athletic Commission are deciding whether to grant him a licence for the showdown.
Khan's US promoter Richard Schaefer said: "I assume we will know by tomorrow (Wednesday). Amir is obviously fully aware of the situation. He is very disappointed but he is going to follow whatever the Nevada Commission is going to rule, and that's where we stand."
According to Schaefer, Peterson tested positive on both 'A' and 'B' samples from a test submitted in March. However, a subsequent, separate test submitted in April was found to be negative.
That negative test is likely to be central to Peterson's case as his legal representatives prepare to plead for the chance to take part in the rematch with Khan, whom he beat in controversial fashion in December.
It is almost inconceivable that there would be time to secure a world-class replacement to face Khan.
Schaefer expressed his anger over his late notice of the positive test, with Peterson's camp having been informed of the findings from the 'A' sample on April 13, with the 'B' result following some weeks later.
Schaefer added: "I got a call from the executive director of the Nevada State Commission who informed us he had seen a letter from VADA [Voluntary Anti-Doping Association] which confirmed Lamont Petersen has tested positive for a substance consistent with the administration of a steroid."
Schaefer continued: "A urine specimen was taken from both fighters on 19 March in an unannounced test following the press conference in Los Angeles.
"The first results of Lamont Petersen's sample were reported to VADA by the lab on 12 April. VADA informed Peterson on 13 April. Why we were not informed is a mystery to me.
"The process of examining the 'B' Sample began at the lab on 30 April - why it took from 13 April to 30 April to test the B sample is again a mystery to me - if I'd been informed I would have asked for expedited testing."
