An "emotionally and physically drained" Mo Farah has withdrawn from Sunday's 1500 metre race at the Diamond League meeting in Birmingham.
The double Olympic champion expressed anger during a news conference on Saturday at how his name has been "dragged through the mud" in relation to allegations that his coach Alberto Salazar has been involved in doping.
A BBC documentary that aired on Wednesday claimed that highly regarded long-distance coach Salazar and one of his athletes, Galen Rupp, had used performance-enhancing methods - something both men have denied.
There has been no suggestion that Farah has been involved in any wrongdoing, and the Somalia-born athlete subsequently stated that he will not part from Salazar unless it is proven that he is guilty and called on the coach to prove his innocence.
The 32-year-old, gold medallist in the 5,000 and 10,000m at the 2012 London Olympic Games, was due to feature in Birmingham, but claims that the off-track distractions have left him unprepared to compete.
"This week has been very stressful and taken a lot out of me. I have not been able to focus properly on Sunday's race and after the events of the last few days feel physically and emotionally drained," he said in a statement.
"I want to run well in the IAAF World Track and Field Championships in Beijing and have decided it is better for me to go back to the United States, seek answers to my questions and get back into training.
"I apologise to the people who bought tickets to come and watch me race and ask for your understanding at this time."