Retired Marine Lt. Col. Oliver North is asking that his Iran-Contra conspiracy trial be delayed six months until March because of this year's presidential election. North, a former White House aide, is scheduled to go on trial Sept. 20 as the first of four defendants charged by the government with various offenses, including conspiracy to illegally divert U.S.-Iran arms-sale profits to the Nicaraguan rebels. "No fair-minded person could argue that this trial should be started seven weeks prior to the presidential election," North's attorney, Barry S. Simon, said in a brief filed in federal court Wednesday. "The intense publicity generated during the final seven weeks of a presidential campaign would deny (North) a fair trial."