Zurich, Switzerland: IAAF President Sebastian Coe admitted Thursday the doping test violations that US sprinter Christian Coleman is alleged to have committed are "not a good story" for the sport.
But Coe told AFP in an interview ahead of the Zurich Diamond League meeting the case showed that missing tests was taken seriously.
Coleman, the fastest man in the world this year over 100 metres, could face suspension after failing to make himself available for three drugs tests over the past 12 months.
It means Coleman would be forced to miss the World Championships in Doha later this year.
"It's not a good story but actually it does show the rest of the world we do take it seriously," Coe said.
"The whereabouts is a very serious element of the anti-doping discussion. I don't want to speculate.
"He's a phenomenal athlete and I will let this process run its course."
The United States Anti-Doping Agency (USADA) says Coleman had been notified of a potential anti-doping rule violation for failing to properly file information about his availability for tests.
A panel is due to hear his case with a decision due by September 5.
Coleman told former Olympic sprinter Ato Boldon in an interview for NBC Sports last week that he was confident he would be cleared.
"I am confident the upcoming hearing on September 4 will clear the matter and I will compete at the World Championships in Doha this fall," Coleman said.
"I'm not a guy who takes any supplements at all, so I'm never concerned about taking drug tests, at any time."
Coleman was second at the 2017 worlds in London behind fellow American Justin Gatlin and has run 9.81sec this year.