Olympic 4x400m relay gold medallist Antonio Pettigrew has admitted to taking performance-enhancing drugs.

Pettigrew, now an assistant track coach at the University of North Carolina, never tested positive during a track career that also earned him World Championship gold over 400m in 1991 and world relay gold in 1997, 1999 and 2001.

Heredia, a former Mexican discus champion and confessed distributor of performance-enhancing drugs on Wednesday testified, however, that Pettigrew had received banned substances from him between 1997 and 2001.

Pettigrew confirmed this was correct when he testified on Thursday, saying that he had been encouraged by Graham to talk with Heredia before purchasing human growth hormone and Erythropoietin (EPO) from the Mexican.

Graham has pleaded not guilty to three counts of lying to federal agents investigating the distribution of performance-enhancing drugs during interviews with them in 2004.

Pettigrew, 40, is one of a number of former athletes who trained under Graham, also including fellow American Olympic gold medalists Marion Jones, Tim Montgomery, Dennis Mitchell and Jerome Young.

He was called to testify before United States District Judge Susan Illston on Thursday having been implicated by main government witness at the trial, Angel 'Memo' Heredia, who has alleged Pettigrew and others received banned, performance-enhancing drugs from him through Graham.

During three hours of testimony for the prosecution, Heredia, 33, had said he had been in regular contact with Graham since an initial meeting in 1996 until the middle of 2001. In that period Heredia testified he advised Graham and his athletes on how to take the drugs and how not to get caught.

He recalled one instance when Graham asked him to send by overnight mail a cocktail of EPO, human growth hormone and insulin for Marion Jones.

A further hour under defence cross-examination on Wednesday saw Graham's lead attorney William P. Keane question the authenticity of FedEx labels addressed to his client.

Heredia insisted his own handwriting was on one of them, even though it appeared to be different from his own style and speculated that the writing of two unidentified people on the other labels belonged to FedEx employees.

The New York Times reported that Judge Illston had declined a request from Keane to remove the FedEx labels from evidence once the jury had been dismissed for the day but had added: "It's not believable testimony."

The trial continues Thursday before resuming next Tuesday for a further three scheduled days after the Memorial Day holiday weekend.