Michael Phelps will not compete at this year's World Championships, according to reports.

The 18-time Olympic champion will make his return to competitive swimming this week after a ban for drink-driving, and has said that he is targeting next summer's Olympics in Rio.

However, USA Today reports that he won't race in Russia this summer as part of his drink-driving punishment.

Phelps told USA Today: "It's obviously very challenging and for me to not be able to compete at World Championships. I will be in full support of everything they do over there, and I wish them all the luck in Kazan."

Phelps retired from the sport after the London 2012 Olympics, but announced his comeback last year.