American track star Allyson Felix is ready to step “out of comfort zone” in her bid to go for a 200-400m double at the World Championships in Daegu, South Korea.

Felix is the reigning three-time world 200m star but has decided to go for what would be an unprecedented fourth title in that event along with the 400m.

“It was a very difficult decision to decide to double.

“I was torn with deciding if I wanted to have fresh legs to defend my title in the 200m for an un-precedented fourth time,” Felix said on the IAAF website.

“Ultimately I decided that I wanted to step outside of my comfort zone and try something different this time.

“I feel blessed to have had success in the 200m at worlds in the past and I felt like it was time to take on a different challenge.

“I’ll also be running in the 4x400m relay in addition to the 200m and 400m.

“I feel like mentally I am going to take one round at a time and physically I feel like I have done the work in practice and I just have to sustain my body the best I can throughout the competition next month.”

Felix last ran competitively more than a month ago at the Diamond League meet in Monaco.

On that occasion she came in second to team-mate Carmelita Jeter in a 200m race.

But she insisted that despite being unhappy at losing, she had the bigger picture on her mind.

“I have my sights set on World Championships and all my training has been geared towards that so at times that means being patient,” she said.