Gatlin will fight on to have his sentence reduced
Olympic 100m champion Justin Gatlin has failed in his appeal to have his four-year drugs ban halved.
The American was hoping the Court of Arbitration for Sport would reduce his sentence which would have allowed him to compete in June's US Olympic trials.
The 26-year-old tested positive for excessive testosterone at the 2006 Kansas Relays.
It was his second doping violation but he insists he has never knowingly taken a performance-enhancing substance.
"I will continue to fight for my right to participate in the great sport of track and field in a time frame shorter than four years," stated Gatlin.
"I have never been involved in any intentional doping scheme."
Cas also rejected an appeal from the world athletics governing body, IAAF, to impose a life ban on Gatlin.
The only change to his four-year penalty was to the start of the term, with Cas pushing it forward from May to July 2006 because that was when Gatlin voluntarily accepted his provisional suspension.
The ban will be completed on 25 July 2010.
We are glad that it has come to a final resolution
The IAAF was happy with the verdict.
"This result demonstrates the IAAF's determination to removethe scourge of doping from our sport," said the body's president Lamine Diack.
"There is no place for doped athletes in our sport."
The US Anti-Doping Agency said the outcome underlined that doping will not be accepted in sport.
"It's another strong reminder that sports are not going to tolerate doping but it is also going to be fair and reasonable in considering all of the factors in giving a sanction of significant magnitude of four years to a sprinter," said USADA chief executive Travis Tygart.
Gatlin based his appeal on the argument that his first failed drugs test, in 2001, should be rescinded because it was caused by a medicine he had been taking since childhood for attention deficit disorder.
Gatlin was suspended from competition for two years but the International Association of Athletics Federations (IAAF), the sport's governing body, reinstated him early in 2002.
The sprinter, however, was told a second offence would result in a life ban, which he only avoided in 2006 because of the "exceptional circumstances" surrounding his first fail and his cooperation with the authorities. He was given an eight-year ban instead.
That penalty was then reduced by a US arbitration panel to four years on 31 December 2007.
USA Track and Field president Bill Roe was relieved that a line could be drawn under the matter.
"This case has been complex and nuanced, and we are glad that it has come to a final resolution," he said.
"Athletes must take responsibility for the substances they put into their bodies, and must choose wisely the individuals with whom they associate."