American sprinting star Gatlin is the world and Olympic 100m champion

The clause allows national anti-doping authorities to either reduce or withdraw sanctions.

But the national body can only do that if it decides an athlete is not at fault for the positive test.

Gatlin's lawyer Cameron Myler said: "We're trying to formulate what our exceptional circumstances are."

Myler was speaking to American newspaper the Mercury News.

She later told the Reuters news agency that she expected a doping review panel to consider Gatlin's case "sometime this week".

The world and Olympic 100m champion will have his case heard by a United States Anti-Doping Agency review board in the first step of the legal process surrounding his case.

The joint world record holder tested positive for elevated levels of testosterone at a meeting in Kansas on 22 April.

Gatlin has denied taking illegal drugs but Myler would not say how they thought the elevated testosterone levels had occurred.

"We certainly have some ideas but we're tracking down the facts," said Myler.

If Gatlin is found guilty he faces a lifetime ban because this is his second positive test.

In 2001 he tested positive for a banned stimulant but his two-year ban was overturned because it was accepted the substance had originated in medicine Gatlin took for attention deficit disorder.