Olympic [Images] sprint champion Justin Gatlin said on Friday he expected to be cleared of doping charges brought against him by the US Anti-Doping Agency (USADA).

The American, in a statement released by his New York publicist, also said he expected to compete again.

"I have put my faith in a system that I believe will clear my name and that I believe will allow me to compete again," the Olympic and world champion and joint 100 metres world record holder said.

The comments were Gatlin's first since USADA announced on Tuesday it had banned him for up to a maximum of eight years pending an arbitration hearing.

Gatlin, 24, announced last month he had tested positive for testosterone or its precursors at the Kansas Relays on April 22.

The hearing process will determine the length of his ban, if any.

Gatlin said he intended to file for arbitration soon.

"I expect when that process is concluded that this entire matter will be resolved favourably," Gatlin said.

Gatlin's shoe company, Nike, has suspended its contract with him until further notice, spokesman Dean Stoyer told Reuters on Friday.

Stoyer said Nike also had terminated its contract with Gatlin's coach, Trevor Graham, who is under investigation by USADA and the International Association of Athletics Federations (IAAF).

A number of athletes coached or previously coached by Graham, including former triple Olympic champion Marion Jones [Images], have tested positive for banned drugs or been charged with doping offences.

Stoyer would not say why Graham's contract was terminated or the reason for the suspension of Gatlin's contract.

Graham's attorney said there was no basis for Nike terminating the coach's contract.

"The contract cannot legally be terminated based upon innuendo and suspicion," Joseph Zeszotarski said in an e-mail to Reuters.

"We hope to avoid having to take legal action but will do so if necessary," he added.

Gatlin said in his statement he still did not know how a banned substance entered his body.