By Matthew Cronin

SAN DIEGO, California (Reuters) - Banned American tennis player Robert Kendrick will appeal to the Court of Arbitration of Sport (CAS) to shorten his 12-month suspension for doping, his attorneys said on Monday.

The International Tennis Federation (ITF) suspended the 31-year-old American last week after he returned a positive test result for methylhexaneamine (MHA) at the French Open.

Kendrick wants his suspension reduced to three months, which would allow him to compete at the U.S. Open starting August 29.

Kendrick claimed he took a pill to help him cope with jetlag without knowing it contained the banned substance.

The ITF wrote in its summary that it did not believe that Kendrick took the substance as a performance enhancer.

However, the Tennis Anti-Doping Program holds players responsible for ensuring no prohibited substances enters their bodies, unless they hold a valid exemption for therapeutic use, which Kendrick lacked.

"A 12-month sanction is shocking, grossly disproportionate to the landscape of MHA and specified substance sanctions in the sporting community," Kendrick's attorney Brent Nowicki told Reuters.

"Robert is not asking to be exonerated. He is asking for a just punishment. Instead, the ITF is trying to take a speeding ticket and turn it into a felony."

Kendrick's attorneys would try to get a CAS hearing the week of August 15, two weeks prior to the start of the U.S. Open, which the player has said would be his last.

The ITF said that Kendrick should have known the rules and took "an inappropriately relaxed approach to his doping responsibilities."

Kendrick reached a career-best ranking of 69 in 2009 and is currently ranked 105th. His suspension runs until May 2012.

(Editing by Ian Ransom)