Christian Coleman, the 100 metres world champion, will miss the Olympic Games despite having a ban for breaking anti-doping whereabouts rules reduced to 18 months.

The American missed three drugs tests in the space of a year and was initially hit with a two-year suspension after a ruling from the Athletics Integrity Unit.

Coleman took responsibility for a first missed test on January 16, 2019, and claimed the second, on April 26 of the same year, was due to a "filing failure".

He said he was only notified about a third missed test in December 2019, the following day. Coleman said he had been out Christmas shopping but had returned during the one-hour window to be tested and questioned why he was not contacted by telephone by the tester.

Coleman took his challenge to the Court of Arbitration for Sport (CAS), which has partially upheld the 25-year-old's appeal.

CAS has ruled Coleman's ban, which was originally due to end on May 13, 2022, will now expire on November 14. It means he will miss the Olympics, which run from July 23 to August 8 in Tokyo.

However, he will be able to defend his world title in Oregon next year.

A CAS statement read: "In coming to its decision, the CAS Panel determined that Christian Coleman had indeed committed an Anti-Doping Rule Violation under Article 2.4 of the World Athletics Anti-Doping Rules, but found the athlete's degree of negligence to be lower than that established in the Challenged Decision: the Athlete was not at home during the 60-minute time slot on the day of the out-of-competition doping control (9 December 2019), as he should have been, and the Athlete should have been on 'high-alert' on that day, given the two existing whereabout failures against him. 

"On the other hand, however, had the Athlete been called by the Doping Control Officer, he would have been able to return to his apartment during the 60-minute window and a test would have been concluded. Although a telephone call during the 60-minute window was not required by the rules, it was nevertheless reasonable for the Athlete to expect such a call, as a matter of standard practice among other Doping Control Officers.

"In conclusion, the CAS Panel determined that an 18-month period of ineligibility was the appropriate sanction in the circumstances."