INDIANAPOLIS - Ryan Murphy said his desire to regain his Olympic 100m backstroke title burns hotter than ever after he punched his ticket to the Paris Games on Monday.

The 28-year-old set an Olympic record when he took gold at Rio 2016 but could do no better than bronze in the event in Tokyo in 2021.

"There's definitely no shortage of motivation from my end," Murphy told reporters after his victory at the U.S. Olympic trials in Indianapolis

"I feel like I've always got a fire under my butt.

"I'm a really motivated person and definitely coming off the last Olympics, I want to win every time I touch the water, whether that's a Monday morning practice or an Olympic finals.

"I want to go to the Olympics and I want to win."

The four-time Olympic gold medallist finished third in the 100m in Tokyo behind to two Russian athletes and made headlines when he said after the race that doping was still a problem in the sport.

He later clarified that he was not accusing the swimmers who beat him of any wrongdoing.

Russian athletes have been unable to compete under their own flag at the Olympics since Rio 2016 after the country was sanctioned for what the International Olympic Committee said was the systematic doping of athletes.

Russia will not be allowed to field athletes in Paris due to its ongoing invasion of Ukraine although individual athletes from Russia and its ally Belarus can compete as neutrals if they meet a strict set of criteria.

The issue of doping raised its head again this year when the World Anti-Doping Agency confirmed reports that 23 Chinese swimmers tested positive for a banned drug before the 2020 Tokyo Olympics but it accepted the country's findings that this was due to substance contamination.

WADA defended its handling of the case but it sparked outrage among athletes and other national doping federations.

Murphy said he has communicated his feeling about the situation to anti-doping authorities.

"I'm definitely behind the scenes expressing my thoughts and learning everything I can about what's going on," he said.

"I'm going to continue to do that."

(Reporting by Rory Carroll in Indianapolis; Editing by Peter Rutherford )