By Steve Keating

OMAHA, Nebraska (Reuters) - After what appeared to be a tormented final chapter to a brilliant swimming career, Michael Phelps returns to the pool at the U.S. Olympic Swim Trials next week looking to pen a new happy ending.

Already with a staggering 22 Olympic medals, including 18 gold, Phelps arrives in Omaha for the June 26-July 3 meet not so concerned about adding a few more podium finishes to his record haul as he is about going out on his own terms.

At the 2012 London Olympics, which he declared to be his last, Phelps won four gold and six medals but walked away filled with the regret that he simply went through the motions rather than embrace the opportunity.

It is a mistake he does not plan to repeat on the road to Rio.

"This is my last chance to do it (right) and I want to do it the way I should have done it in 2012," said Phelps. "I think if I were to look back 20 years later at London, I would have been disappointed in myself, that I let myself down for how I prepared.

"That is something I never want to live with."

The American said he lacked fire.

"Going into 2012 was like pulling teeth, it was brutal. I could barely get to the pool.

"It was really hard to keep motivated going into 2012 and it is the exact opposite now. I feel like a kid again, I am happy doing what I'm doing," said Phelps.

Phelps made his Olympic debut at the age of 15 in the 2000 Sydney Olympics, failing to win a medal, but in three Summer Games since has gone on to become the most decorated Olympian ever.

Now 30, married with an infant son and bidding for a berth on his fifth U.S. Olympic team, Phelps's Rio program is far less ambitious than in 2008 at the Beijing Games where he claimed eight golds from eight events.

In Omaha, Phelps is scheduled to swim five events: the 100 metres and 200m butterfly, the 200m individual medley, and the 100m and 200m freestyle.

Phelps is not expected to contend for a berth in either of the freestyle events but will likely attempt to post a top time in the preliminaries that will establish him as one of the four fastest in order to lock up a relay spot.

Yet once again, Phelps will be the headliner at the week-long trials which have sold out every session at the Century Link Center, where a portable pool has been installed inside the 13,000-seat arena.

The meeting will also feature a glittering golden supporting cast that includes Phelps' great rival Ryan Lochte, Missy Franklin, Katie Ledecky and Natalie Coughlin, bidding to become the most decorated U.S. female Olympian.

Five-time Olympic gold medalist Lochte will swim the 400m individual medley as reigning Olympic champion, plus the 100m and 200m freestyle, 200m backstroke, 100m butterfly and the 200m individual medley.

Franklin, the Olympic champion in both the 100m and 200m backstroke, will try to secure a spot in those two events as well as 100m and 200m freestyle.

Few will be busier than Ledecky, who could bid to become the first U.S. woman to swim the 100m, 200m, 400m and 800m freestyle at a single Olympics.

The 33-year-old Coughlin, tied with Jenny Thompson and Dara Torres as top U.S. Olympic medals winner among women with 12, will try to qualify in the 50m and 100m freestyle.

(Editing by Larry Fine)