Armstrong's return from cancer to win the Tour a record seven consecutive times made him a hero to cancer patients worldwide and elevated cycling to an unprecedented level in America.
The Tour "is the intention," Armstrong's spokesman Mark Higgins told The Associated Press, "but we've got some homework to do over there."
Added Bill Stapleton, Armstrong's lawyer and longtime confidant: "We're not going to try to win second place."
What team he'll ride with and in what other races he'll compete are undecided, Higgins said.
"I am happy to announce that after talking with my children, my family and my closest friends, I have decided to return to professional cycling in order to raise awareness of the global cancer burden," the 36-year-old Armstrong said in a statement released to The Associated Press. "This year alone, nearly eight million people will die of cancer worldwide. ... It's now time to address cancer on a global level."
In an exclusive interview with Vanity Fair, Armstrong told the magazine he's 100 percent sure he's going to compete in the Tour de France next summer. "I'm going back to professional cycling," he said in the story posted Tuesday on the magazine's Web site. "I'm going to try and win an eighth Tour de France."
On Monday, the cycling journal VeloNews reported on its Web site that Armstrong would compete with the Astana team, led by close friend John Bruyneel, in the Tour and four other road races the Amgen Tour of California, Paris-Nice, the Tour de Georgia and the Dauphine-Libere.
But there are no guarantees Astana would be allowed to race in the 2009 Tour. Race officials kept the team out of the 2008 Tour because previous doping violations.
Armstrong's return to competition raises the question of whether he risks damaging his athletic legacy. And his own words likely will cause some to wonder if he'll approach his return with the same steely-eyed determination and passion.
In an interview published in the October issue of Men's Journal, Armstrong said, "I'm glad I'm not cycling anymore ... It was fun while it lasted, and I liked it, but I'm so focused on other things now that I never think about it."
He's certainly thinking about it now.
With his riveting victories over cancer and opponents on the bike, to his work for cancer awareness and gossip-page romances, Armstrong has become a modern-day American icon.
He was an established sprint champion when he was diagnosed in 1996 with testicular cancer that had spread to his lungs and brain. Doctors gave him less than a 50 percent chance of survival.
Surgery he has a half-moon scar on his head from the brain operation and brutal cycles of chemotherapy saved his life. From there, it was determination and powerful self-discipline that led him back to the bike.
His stunning win at the 1999 Tour de France was just the start. Under the guidance of close friend and U.S. Postal Service team director Bruyneel, Armstrong morphed from a sprinter into a technical expert who could climb mountains at speeds that punished other riders.
Armstrong's goal every year was to win the Tour de France, the sport's biggest race, and he dominated the Pyrenees and Alps like no other rider ever had.
The victories also forced him to defend himself against skeptics who questioned whether he was cheating by using performance-enhancing drugs. He got in several public spats with officials at the World Anti-Doping Agency.
While many riders were caught doping, Armstrong never tested positive and has always maintained he was a clean rider, using hundreds of passed drug tests during his career as proof.
His Lance Armstrong Foundation has raised hundreds of millions of dollars for cancer awareness and survivorship. The foundation's yellow "Livestrong" wristbands that started selling in 2004 are still seen everywhere with many copycats.
He retired after his 2005 Tour de France victory, diving head first into making cancer a political issue and causing some to ask if he may someday run for office himself.
"This is a damn war for me. It's nothing other than that," Armstrong told The Associated Press in 2007. "I had the disease and I hate it and I hate that we haven't made enough progress against it."
Armstrong has lobbied for cancer treatment funding in Washington, D.C., co-hosted televised cancer forums with presidential candidates and was instrumental in 2007 persuading the Texas Legislature to approval a $3 billion fund for cancer research. He can rally millions of his "Livestrong Army" through his Web site to support cancer causes.
His social life has done just as much to keep him in the spotlight.
After his divorce from wife Kristin, the mother of his three children, Armstrong has had high-profile relationships with rocker Sheryl Crow, fashion designer Tory Burch and most recently, actress Kate Hudson.