Legendary swimmer Michael Phelps is to come out of retirement ahead of a possible crack at another Olympic campaign.

The American will compete for the first time since London 2012 in a meeting in the US state of Arizona next week.

Phelps is the most decorated athlete in Olympic history, with 18 gold medals, and 22 overall.

He returned to training last year, and the 28-year-old is now being tipped for the 2016 Olympics in Rio.

He will make his first competitive appearance in two weeks at the Arena Grand Prix.