RAKVERE, Estonia (AP):

Returning from a four-year doping ban, Justin Gatlin says he's running for his fans, friends and infant son.

The 28-year-old American will be running in the 100 metres today at a small track meet in Estonia and said he expects to compete in the Olympics in two years' time.

"I think of myself as a championship athlete," Gatlin said Monday. "I can't wait for London 2012.

Asked whether he would be able to run under 10 seconds, Gatlin would only say he is "ready to be fast."

"I don't only run for myself. I run for my family, my fans and my friends. I want to go out there and be able to show my son that I'm a good athlete."

Gatlin won gold in the 100 metres at the 2004 Athens Olympics and in the 100 metres and 200 metres at the 2005 world championships in Helsinki. He tested positive in April 2006 for excessive testosterone.

Gatlin claims he doesn't know how a banned substance got into his system.

"I went through all the phases: depression, anger," Gatlin said. "Right now, I'm just really more calm."

He was formerly coached by Trevor Graham, who was given a lifetime ban by the U.S. Anti-Doping Agency for his role in helping athletes obtain performance-enhancing drugs. Graham also coached dopers Marion Jones and Tim Montgomery.

Gatlin is now training under speed technician Loren Seagrave, who once worked with former world record-holder Donovan Bailey. Seagrave said Gatlin's technique in the race will be more important than his time.