Johnson's agent, Morris Chrobotek, confirmed yesterday to Canadian press, the National News Agency, that Johnson had tested positive for a banned diuretic in October, but said it was taken for medical reasons to assuage severe pain.

Chrobotek said the test result was leaked before the Canadian Centre for Ethics in Sports (CCES) had decided whether it constituted a doping infraction.

The Johnson camp is paying the Ottawa-based CCES for two tests a year while the disgraced sprinter continues his bid to return to competition.

Diuretics are banned because they can mask performance-enhancing drugs. ``How can you cheat when you're not even allowed to run?'' Chrobotek said.Johnson, banned from competition for life in 1993 after a second positive doping test, turns 38 in December.

But the Jamaican-born sprinter continuesto train despite the fact that his appeal to return to competition was rejected by the world athletics governing body earlier this year. This summer Johnson announced plans for an anti-drug foundation.