"The fight's far from over," he told The Associated Press. "Obviously, yesterday was very disappointing. Myself, my family, all my sponsors and my teammates were shocked."
The independent American Arbitration Association-North American Court of Arbitration for Sport handed down the suspension Monday, citing a blood-doping violation discovered at a race in September.
He can return to competition April 17, 2007, but he forfeits all competitive results since Sept. 11, 2004, the day of the positive test at the Spanish Vuelta.
Positive test at the Olympics
The positive test occurred a month after Hamilton won the time trial at the Athens Olympics. Hamilton allegedly tested positive in Athens, but that case was dropped. Nonetheless, the Russian Olympic Committee filed an appeal with the Court of Arbitration for Sport seeking to strip Hamilton of his gold medal and give it to silver medalist Vyacheslav Ekimov.
U.S. Olympic Committee spokesman Darryl Seibel declined to comment on Hamilton's suspension and said he didn't know the status of the Russian appeal.
Hamilton said he expected the arbitrators to rule in his favor.
"I'm certainly not a quitter and I'm not going to give up until I'm vindicated," he said. "My chances of racing in this year's Tour de France are slim to none. That's what got me out of bed every morning."
The arbitration panel ruled that Hamilton's positive sample was from a transfusion of another person's blood. That would increase Hamilton's red-blood-cell count, increasing his endurance, the U.S. Anti-Doping Agency said.
Based on blood tests done in spring and summer 2004, cycling's international governing body, Union Cycliste International, had warned Hamilton and his Phonak team that he was under suspicion.
"UCI took the necessary action to protect the integrity of its sport," said Terry Madden, USADA's chief executive officer. "This decision shows that sport is committed to protecting the rights of all clean athletes and that no athlete is above the rules."
Hamilton first tested positive for blood doping after winning the time trial at the Athens Olympics in August, according to the International Olympic Committee. The case was dropped after his backup sample was frozen, leaving too few red blood cells to analyze.
Prosecutors in Athens alleged in December that a doping laboratory destroyed Hamilton's blood sample.
The UCI denied Phonak a racing license last fall because Hamilton and two other team riders had been charged in drug cases in the previous three months. Hamilton said Phonak successfully appealed the decision in December and will be able to compete in the Tour de France and other UCI Pro Tour events this year.
Phonak fired Hamilton in November, nearly a year before his contract was set to expire. He said at the time that he agreed to leave to improve the team's chances of competing on the pro tour.
Hamilton was considered a possible successor to six-time Tour de France winner Lance Armstrong. The two were once teammates on the U.S. Postal Service team. Hamilton finished fourth in the 2003 Tour despite a broken collarbone.
Hamilton earned a six-figure salary with Phonak and has endorsement deals with Nike, Oakley and other sponsors.