UPDATE 3-Doping-U.S. sprinter Gatlin's ban appeal rejected

(adds detail, reaction)

By Martyn Herman

LONDON, June 6 (Reuters) - Olympic 100 metres champion Justin Gatlin failed to have a four-year doping ban overturned by the Court of Arbitration for Sport (CAS) on Friday.

The CAS decision means the 26-year-old will not be able to compete in the U.S. Olympic trials in June and will not defend his crown in Beijing.

"While I am pleased that the arbitrators rejected a life ban, 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," Gatlin, who is banned until July, 2010, said in a statement issued by his attorney.

Gatlin was given a four-year ban by an American Arbitration Association panel in January after he tested positive for the male sex hormone testosterone in 2006.

The longer ban was imposed because it was deemed to be his second offence after he failed a doping test in 2001 because of an amphetamine contained in a medication he had taken since a child for Attention Deficit Disorder.

Gatlin's attorney Maurice Suh maintained his client's original positive in 2001 should not have been used to increase the 2006 punishment because the International Association of Athletics Federations (IAAF) ruled he had not intentionally committed a doping offence and he had been reinstated after a year.

Had the U.S. panel not considered the 2001 test, Gatlin would probably have received a two-year ban as a first-time offender and could have been eligible for the U.S. trials.

In making their decision CAS also altered the start date of Gatlin's period of ineligibility from May 25, 2006 to July 25, 2006 -- the date when he voluntarily accepted a provisional suspension.

NO LIFE BAN

All his results for the three-month period from April 22, 2006, when his sample was taken, will be voided.

CAS rejected a call from the IAAF to impose a life ban on Gatlin, but his career now looks to be in tatters.

"I have never been involved in any intentional doping scheme," Gatlin said on Friday. "And I think that CAS would not have rejected the IAAF's position unless it also believed that I had not participated in any intentional doping."

Suh, who also defended disgraced U.S. cyclist Floyd Landis, said they had not decided on the next step.

"Right now, Mr. Gatlin is weighing his other legal options," Suh said in a statement. "We do not have the reasoning of the ruling from CAS yet.

"From the ruling, it appears that CAS has adopted our position that proportionality should apply in sanction cases. Obviously we had hoped that the panel would have found that proportionality would have demanded a lower sanction."

Former 100m and 200m world champion Gatlin's demise is another blow for U.S. Track and Field which has been hit by several high-profile doping cases in recent years.

However, U.S. Anti-Doping chief executive Travis Tygart told Reuters in a telephone interview that Gatlin could still return to the sport.

"It's another strong reminder that sports are not going to tolerate doping but it is also going to fair and reasonable in considering all of the factors in giving a sanction of significant magnitude of four years to a sprinter," he said.

"It's not a lifetime ban. He'll certainly be able to compete again in two years when it's up in July of 2010. He'll have time to compete again and he'll certainly have a career in coaching assuming there are no other violations.

"We think it (the sentence) was appropriate given all of the circumstances of the case."

U.S Track and Field president Bill Roe said they respected the CAS decision and it was time to move on.

"We are now looking ahead, focusing on the Team USA squad for the Olympic Games that will be chosen at the Olympic Trials," he said.

"These are the athletes who will take track and field into a brighter present and future."

(additional reporting by Gene Cherry, Steve Ginsburg and Mark Lamport-Stokes; editing by Miles Evans)