Beijing, Feb 4: Maurice Greene sprang a little surprise on Monday - he's retiring. The former Olympic and world champion cited nagging injuries for his decision, making the announcement half way around the globe and not long after the Super Bowl had ended in Glendale, Arizona.

"Today is my official day of announcing my retirement," he said in Beijing, sitting down for an interview with 'The Associated Press'.

"You're the first I've told it to."

Traveling in China inspecting Olympic facilities with a group of contenders for Olympic gold, the 33-year-old Greene said injuries forced him to retire. Coaching and business interests in the U.S. will now be his focus.

"It's a little sad for me but it's happy at the same time because I've had a great career. I've done a lot of great things," Greene said.

"For the last couple of years, I've had nagging injuries that have stopped my training. So I think it's better to just call it quits."

From Kansas City, Kansas, Greene was the dominant sprinter of the late 1990s and into the new century. He set a world record for 100 meters in 1999 and won the same sprint at the Sydney 2000 Olympics.

He also won world championship 100 titles in 1997, 1999 and 2001. At Seville in '99 he also won the 200 and 4x100 relay golds in a rare triple.