Michael Phelps will be back for Rio Olympics, says Ryan Lochte

US Olympic swimming star Ryan Lochte says he has no doubt superstar Michael Phelps will end his retirement and return to the pool for another shot at Olympic glory at the 2016 Rio Games.

Speaking in Vancouver on Wednesday where he is swimming in a local meet this weekend, the 28-year-old Lochte, winner of 11 Olympic medals and holder of three world records in the individual medley, told media it's not a question of if the 27-year-old Phelps will return but when, reports Xinhua.

"Michael Phelps is the hardest racer I ever went up against, and what he's done for this sport of swimming is tremendous," he said. "I hope he comes back in. I think he will. I know he will. It's just a matter of time and when. I know he will."

Lochte wouldn't say if he had talked to the winner of a record 22 Olympic medals who announced his retirement last year following the London Olympic Games.

"I can't say. I just have a feeling. I'll just leave it at that. I have a feeling he'll come back," he said, adding that the sport would be better with Phelps's return.

"Racing him (Phelps) was one of the biggest challenges in my swimming career and I loved it. I've gotten to the point where it was one of his biggest challenges too and just the friendship that we've developed throughout the years of racing each other and the rivalry it's one of the biggest in the sport and we had a lot of fun doing it. So I definitely hope he comes back because in a way he pushed me and I pushed him. So it was definitely great for the sport," he said.