Los Angeles - United States sprint star Christian Coleman could face suspension after failing to make himself available for three drugs tests, multiple reports said Thursday.
Coleman, 23, the fastest man in the world over 100 meters this year and the favourite for next month's World Championships in Qatar, has missed three separate tests in the past 12 months.
Britain's Daily Mail and The Times newspaper reported that Coleman, a late withdrawal from last Sunday's Diamond League meeting in Birmingham, is challenging one of the alleged "whereabouts" failures.
Under internationally recognised anti-doping rules, athletes are required to make their exact whereabouts known to drug-testers up to 90 days in advance in order to facilitate out-of-competition testing.
Athletes who fail to make themselves available for three drug tests are treated the same as athletes who fail a drug test and face an automatic suspension.
Any suspension of Coleman would represent another bodyblow against athletics just as the sport attempts to move on from the Russian doping scandal.
Coleman, the world record holder over 60m and world indoor 60m champion, has emerged as the most likely successor to Usain Bolt following the Jamaican sprint king's retirement in 2017.
Coleman was a silver medallist at the 2017 World Championships in London behind mentor Justin Gatlin, and has a personal best of 9.79sec. He has the quickest 100m time of 2019 with a world leading 9.81sec set in Stanford, California in June.
The circumstances of Coleman's alleged missed tests were not revealed.
Coleman's agent, Emanuel Hudson, did not immediately respond to a request for comment.
The United States Anti-Doping Agency, meanwhile, would not confirm a case involving Coleman.
"In general, for any potential violation a full investigation will be conducted and the case must be resolved before information is made public by USADA," a spokesman told AFP.
Depending on the dates of Coleman's missed tests, if confirmed, he could miss the world championships and the 2020 Tokyo Olympics.
Other athletes who have been suspended following three missed drugs tests include 2016 Olympics 100m hurdles champion Brianna Rollins-McNeal.
Rollins-McNeal was banned for a year by USADA after missing three tests in 2016 -- two of them after she forgot to update her whereabouts details while attending a fete in in her honour held in her hometown and another when travelling to the White House to meet President Barack Obama for a reception.
However some athletes have successfully staved off a possible suspension after three missed tests. In 2016, British cyclist Lizzie Deignan, then Lizzie Armitstead, escaped suspension after taking her case to the Court of Arbitration for Sport.
Deignan argued that one of her three missed tests should be declared invalid because a doping control officer had not followed procedures correctly and tried hard enough to locate her.
Coleman's failure to notify testers of his whereabouts was greeted with scepticism by US distance runner Kara Goucher on Thursday.
"Missing 3 tests in a 12 month period is bad," Goucher wrote.
"You can literally text an update of your location at any time. Will be interesting to see if he is able to dispute one of the missed tests."