(Reuters) - Justin Gatlin may be the world 100 meters champion with a decade of experience behind him, but the American says he is feeling like a rookie again.

2016 Rio Olympics - Athletics - Semifinal - Men's 200m Semifinals - Olympic Stadium - Rio de Janeiro, Brazil - 17/08/2016. Justin Gatlin (USA) of USA reacts. REUTERS/Lucy Nicholson. Picture Supplied by Action Images

A trip to South Africa is firing up the top-ranked sprinter, he told Reuters.

“I’ve never been to South Africa, I’ve never run a competitive 150 and I’ve never run this early when I didn’t compete indoors,” Gatlin said in a telephone interview from his Florida home.

All that changes on Thursday when the 2004 Olympic champion competes in the Athletix Grand Prix Series in Pretoria, South Africa.

“It’s exciting,” said the American, not long past his 36th birthday. “You get that nervousness but also excitement. It makes you feel like a rookie again.

“I actually jumped at the opportunity when my agent called. We’ve got hundreds of 100 meters to run and we can run a 200 anytime so I said let’s run a 150. Let’s go out there and see what it feels like.”

There is no official record in the infrequently contested event, but retired Jamaican 100 and 200 meters world record holder Usain Bolt set the world best, a flashy 14.35 seconds he ran at Manchester, England in 2009.

Gatlin would not speculate on how fast he might run.

“I am just going to zone in on my technique to be as competitive as possible,” he said, adding he is dedicating the race to the Atlanta-based Rally Foundation for Childhood Cancer Research with whom he is now partnering.

His only 150 meters have come in training.

SPEED ENDURANCE

No longer an indoors competitor, Gatlin admitted he was not at top speed yet.

“We’re in speed endurance time right now,” the 2005 and 2017 world champion said of workouts with coach Brooks Johnson who is mentoring Gatlin again.

“We’re just getting to the speed phase so it’s not like we are incredibly fast when it comes to racing right now.”

His first 100 meters will not likely come until the Shanghai Diamond League meeting in May.

“I’ll just jump in relays and work on speed,” Gatlin said of his plans after the South Africa trip.

Somewhere along the way - on or off the track - he is likely to meet up with America’s newest sprint standout, 60 meters world record holder Christian Coleman.

They chat frequently and both attended the University of Tennessee where they were multiple collegiate champions.

“He’s amazing when it comes to his transition,” said Gatlin. “He’s strong, he’s focused and there is something that you see in him that you don’t see in a lot of other athletes. It’s that hunger to be the best.

“When he comes across the line even if he wins a round, you can look at the disappointment on his face because he didn’t run as fast as he wanted to.

“He is constantly trying to be a better athlete, not just settling. That’s the kind of athlete that stay around for a long time.”