Marathon world record holder Eliud Kipchoge compete at the world championships in Doha later this year.
Instead the Kenyan has opted to focus on his bid for a second Olympic gold medal at Tokyo 2020 where he is likely to compete against his rival at the Virgin London Marathon Mo Farah.
Farah is expected to contest the 10,000m at the worlds rather than running the 26.2-mile distance, with the race starting after midnight because of the heat.
Kipchoge has not competed at a World Championships since 2011, when he switched to the marathon.
Since then he has become the quickest marathon runner of all time.
He has won 10 of his 11 marathons and is a strong favourite for a fourth title in London against Farah, who finished third last year.