Michael Phelps, the most decorated Olympian of all time, marked his return to competitive swimming on Thursday by posting the quickest time in qualifying for the men's 100 metre butterfly at the Arena Grand Prix in Mesa, Arizona.

The 28-year-old has not raced since the London 2012 Games, but lay down the marker for United States rival Ryan Lochte with a time of 52.84 seconds - in the 14th and final heat - to ease into the final later in the day.

Five-time Olympic gold medallist Lochte was the second fastest qualifier in 52.94secs.

Phelps has won 22 Olympic medals, including 18 golds, and also holds the world and American national record for the 100m butterfly.