Michael Phelps qualifies for Olympic Games in Rio

Michael Phelps has qualified for his fifth Olympic Games

Michael Phelps has qualified for his fifth Olympic Games after winning the 200m butterfly event at the US swimming trials for Rio.

The American, whose record 22 Olympic medals include 18 golds, won with a time of 1:54.84 to secure qualification, holding off the determined Tom Shields, who took second in 1:55.81.

Phelps, 31, had said London 2012, where he won four gold and six medals overall, would be his last Games but his retirement was brief.

However, his comeback was disrupted by a drink-driving arrest followed by a stint in rehab.

"With everything that's happened, being able to come back - this was probably harder than any swim I've had in my life," Phelps said. "I'm checking a box off, being able to get on the team.

"I didn't feel good the first two swims, didn't really feel that good tonight. But getting on the team was the most important thing, and that's the only thing I had to do tonight."

Despite his medal haul in London four years ago, Phelps said he was motivated to come out of retirement to finish his career on his terms.

"Coming back and being able to have the opportunity to finish how I want," he said. "I'm doing this because I wanted to.

Phelps was succesful at the 2016 US Olympic team swimming trials

"Thinking about the ups and downs we've gone through in and out of the pool to get to this point and not feeling an absolute 100 per cent but still being able to get the job done.

"I think things are probably going to hit me a lot more emotionally now than what they would have in the past, because I'm enjoying the moment and I'm embracing the moment."

Regaining the 200m butterfly Olympic title he surrendered to Chad le Clos in London, in an event he long considered his speciality, is also a strong motivator for Phelps in Rio.

"I've definitely thought a lot about that race," Phelps said, adding that he hadn't brought himself to watch it back until recently.

Phelps won four gold medals at the London 2012 Games

"I know there's a lot that I did in that race that I'm not going to do again, and I think I'm a lot more prepared this time than I was last time. I'm looking forward to having the chance to race him this summer."

However, le Clos will not be the only man standing in his way in the 200m fly, with Hungary's Laszlo Cseh, Japan's Daiya Seto and Masato Sakai topping the world rankings.

"We have a little over 30 days to prepare," said Phelps, who is also chasing Olympic berths in the 100m fly and 200m individual medley.

 "Just looking forward to hopefully swimming faster than what I swam here."