Lance Armstrong won seven consecutive Tours from 1999-2005
Cycling legend Lance Armstrong is coming out of retirement to try to win an eighth Tour de France in 2009.
The American, who will be 37 on 18 September, recovered from cancer and claimed victory in the Tour a record seven times before retiring in 2005.
He said: "I'm happy to announce that after talking with my children, family and closest friends, I have decided to return to professional cycling.
"It is in order to raise awareness of the global cancer burden."
He added on his website on Tuesday: "This year alone, nearly eight million people will die of cancer worldwide. It's now time to address cancer on a global level."
Armstrong famously overcame an aggressive form of testicular cancer before embarking on his remarkable run of Tour de France victories.
Since his retirement in 2005, he has run respectable times in the New York and Boston marathons but much of his energy has been spent running the Lance Armstrong Foundation, a charity dedicated to combating cancer.
Armstrong had to return to the United States Anti-Doping Agency's (USADA) testing programme to compete in last month's Leadville Trail 100 mountain bike race in Colorado.
He finished a creditable second in the tough event, to show he remains in good shape but the Texan is unlikely to settle for that at next year's Tour.
Armstrong will announce details of his team and pre-Tour racing schedule on 24 September at the Clinton Global Initiative in New York City.
When I'm on the bike I feel just as good as I did before
"I think it's great," said Armstrong's former team-mate George Hincapie.
"Without Lance, half the teams in the Tour probably wouldn't be around. He's done more than anyone for the sport especially in America and around the world."
Armstrong gave more detail of his return in an interview with American magazine Vanity Fair's website VF.com.
He appears to have been inspired by some of the older competitors at the 2008 Olympics, as well as what he believes was a slow pace of this year's Tour de France.
"Look at the Olympics," said Armstrong, who gave the interview to the website over three days in late August.
Armstrong (right) returned to competitive action in a recent mountain bike event
"You have a swimmer like Dara Torres, who claimed silver. Even in the 50m freestyle, a 41-year-old mother proved you can do it.
"Constantina Tomescu-Dita won the marathon and she was 38.
"Older athletes are performing very well. Ask serious sports physiologists and they'll tell you age is a wives' tale.
"I'm not going to lie. My back gets tired quicker than it used to and I get out of bed a little slower than I used to.
"But when I'm on the bike I feel just as good as I did before."
Nevertheless, Armstrong will have to buck a clear historical trend if he is to win a remarkable eighth Tour title, with only the 36-year-old Firmin Lambot - back in 1922 - winning the Tour beyond the age of 34.
During his career, many other riders were caught doping but Armstrong has never tested positive and has always maintained he was a clean rider, using hundreds of passed drug tests during his career as proof.
In 2006, an independent investigation by the International Cycling Union cleared Armstrong of any doping in his first Tour victory.
"There's this perception in cycling that this generation is now the cleanest generation we've had in decades, if not forever," said Armstrong.
"And the generation that I raced with was the dirty generation.
"I'll be totally honest with you. The year that I won the Tour, many of the guys that finished second through to 10th are gone. Out. Caught. Positive tests. Suspended. Whatever.
"And so I can understand why people look at that and go, 'well, they were caught - and you weren't?'
"So there is a nice element here where I can come with really a completely comprehensive program and there will be no way to cheat."
Armstrong has also hit the headlines and gossip columns for his private life since divorcing his wife Kristin, the mother of his three children, with high-profile relationships with singer Sheryl Crow, fashion designer Tory Burch and actress Kate Hudson.
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