BBC SPORT | Athletics | Injuries force Greene to retire

The 33-year-old American sprint star has been plagued by injury in the last two years and has now decided to pursue coaching and business interests.

"It's a little sad for me but I've had a great career. Because of my injuries, it's better to call it quits," he said.

Greene had been expected to compete in the 100m, 200m and 4x100m races at this year's summer Olympics in Beijing.

But he said: "I don't think I can have that mental battle with myself coming back from injury any more. It takes a lot out of you mentally... you start getting down and then you get depressed.

"This is Olympic year, something I wanted to do so bad. So I just decided to call it quits... I want other people in the sport to shine."

The Kansas native has been one of the sport's dominant figures over the past decade, winning the 100m world championship in 1997, 1999 and 2001.

He also took gold in the 200m and 4x100m relay in 1999, placing him alongside Tyson Gay and Carl Lewis as one of only three men to win triple gold.

Greene triumphed in the 100m at the 2000 Sydney Olympics, he also anchored the victorious men's 100m relay team and he still holds the indoor 60m world record of 6.39 seconds.

However, his last wins on tour came in the 2004 season, with the likes of Asafa Powell and Gay dominating the sport in recent years.

"It's a shocker to me," Gay told reporters. "Not having Maurice Greene around in track and field any more is just like Michael Jordan retiring from basketball, or Tiger Woods retiring.

"He's the greatest."