Former Olympic champion Gatlin announces retirement

US sprinter Justin Gatlin has announced his retirement from athletics after a career that included an Olympic gold medal, several world titles and a pair of doping bans.

The three-time Olympian whose bid to qualify for last year's Tokyo Games ended when he aggravated a hamstring injury during the US trials, made the announcement in a social media post late on Thursday.

"Through all my ups and downs, victories and losses, I have loved you track," Gatlin wrote in the post on his 40th birthday.

"You gave me tears of sadness and of joy, lessons learned that will never be forgotten.

"I'm grateful for our relationship and the many others that I’ve had along the way. The torch is passed but the love will never fade. On your mark, get set ... Gone!"

Gatlin won the 100 metres gold medal at the 2004 Athens Olympics and a year later at the world championships in Helsinki achieved the 100m and 200m sprint double.

He went on to win 100m gold at the 2017 world championships and gold in the 4x100 relay two years later in Doha.

Gatlin's first drugs violation came in 2001 when he tested positive for an amphetamine contained in attention deficit disorder medication he had taken since his youth.

Talk of that suspension might eventually have faded or been downplayed until he failed a test for the banned steroid testosterone in 2006.

The American was banned for four years and many thought that would be the end of his career.

But to the ire of many, Gatlin remained a force when he was eligible to run again in 2010.

Gatlin has never admitted to doping and continued to insist his 2006 test came from a massage therapist rubbing testosterone cream onto his legs, a contention the therapist has denied.

"Looking toward the future, I want to live a legacy that continues to inspire others," wrote Gatlin.

"Turning one year older and shifting my energies into new career endeavors, I hope to continue to inspire those who have supported me throughout my whole career."