Irish 10,000m runner Cathal Lombard has admitted taking the banned blood-boosting substance EPO.
The 28-year-old, who has failed a test for the drug, had qualified for the 10,000m and 5,000m events in Athens.
"At the moment, subject to looking at all the information, I would be unlikely to contest the findings," Lombard told the Irish Examiner.
"I am saying this was the case and this is what I did and, hands up, I did it. There was nobody else involved at all."
Lombard claimed he took the drug because
it was the only way to keep up with other athletes, but
said he had been "naive" to think he could cover it up.
"I didn't set out to try and win medals or to make money.
"I just wanted to be as competitive as I could and have an equal chance with everyone else."
The positive result is believed to have come from an out-of-competition test carried out
in Switzerland on 11 July.
The 28-year-old faces expulsion from the Irish Olympic team and a
ban of up to two years.
"My eyes were really opened from conversations I had with people on the professional scene," added Lombard.
"I looked at some of the times being consistently run and I asked myself if this was possible naturally.
"The only logical conclusion I could reach was that, in a
lot of cases, the answer was definitely 'no'."
Lombard said he had acted alone.
"I realise now that most of the people I'm speaking about on the professional scene are operating on a very
sophisticated basis, with proper medical back-up and advice on how not to get caught.
"In comparison I was merely dabbling and made no attempt to cover it up."
Lombard's dramatic improvement over the last 18 months was highlighted by a Irish 10,000 metre record in April when his time of 27:33.58 cut 13 seconds off Mark Carroll's previous mark.
The athlete will formally answer the charge at an Athletics Ireland hearing in Dublin on Tuesday.