Veteran US sprinter Justin Gatlin set his sights on winning another Olympic gold at the Tokyo Games on Sunday -- then refused to rule out continuing his career into his 40s.

The 39-year-old will become the oldest man ever to win an Olympic track medal if he makes the podium at this summer's coronavirus-delayed Tokyo Games.

And with former archrival Usain Bolt now retired and reigning world 100m world champion Christian Coleman banned from the Tokyo Games for missing three doping tests, Gatlin said he believes he has a realistic chance.

"I hope so -- That's why I'm still here," he said after competing at a test event held behind closed doors at Tokyo's Olympic Stadium.

"I love making Olympic teams, but I'm not in it for the free trip. I want to be able to work hard and get on top of that podium again at some point, and I hope this year is that year for me."

Gatlin won 100m gold in Athens in 2004 but was forced to miss the 2008 Games because of a suspension for drug offenses.

He won bronze in 2012 and silver four years later, and said Sunday that Tokyo would be his "fourth and last Olympics" if he makes the US team.

But he quickly changed tack when asked if he would definitely hang up his spikes this summer.

"I'm saying it right now, but obviously the way my career's going, I don't know," he said.

"I'm happy with where I'm at. I'm still hungry for competition, so I won't say never."

Justin Gatlin of the US has set his sights on winning another Olympic gold at the Tokyo Games -- and won't rule out continuing his career into his 40s
Justin Gatlin of the US has set his sights on winning another Olympic gold at the Tokyo Games -- and won't rule out continuing his career into his 40s AFP / Charly TRIBALLEAU

Gatlin won Sunday's 100m race in a time of 10.24sec, and said he was satisfied with his form as he looks ahead to next month's US trials.

But he conceded that the Games would "definitely be different" with strict virus countermeasures in place, and that "a lot of athletes are not going to be happy" with rules restricting their movement.

"I just miss going out -- going to local dineries and eating the local food," he said.

"Hopefully by the time the Olympics come around, it will be just a little more lenient about where we can go."

Sunday's event was held behind closed doors, with Tokyo currently under a virus state of emergency, and Gatlin described the atmosphere inside the cavernous stadium as "weird".

Olympics organisers will decide next month how many -- if any -- fans can attend the Games, and Gatlin believes athletes will have to "bring their own energy to the track".

"For all the athletes that are going to come, they have to come with their focus on level 10," he said.

The Tokyo Games will be the first Olympics since Gatlin won gold in 2004 not to feature three-time 100m champion Bolt.

But Gatlin is taking nothing for granted with his former rival now out of the picture.

"Before, it was Usain and me going head to head and knowing exactly what was going to happen," he said.

"Now, you've got to keep your head on swivel, because anybody can come up."