OCEANSIDE, Calif., Feb 8 (Reuters) - A U.S. Marine, who had admitted firing several rounds at an Iraqi grandfather after his unit kidnapped the man, asked a military court on Thursday to withdraw his guilty plea. Cpl. Trent Thomas, 25, pleaded guilty on Jan. 18 to murder, conspiracy, larceny housebreaking, kidnapping and lying to investigators about the incident. But as a military court was considering his punishment at Camp Pendleton north of San Diego, his lawyer abruptly requested that the plea be removed.