WASHINGTON - A jailed American Muslim leader and a Libyan intelligence agent have told U.S. and Saudi authorities they were involved in a Libyan plot to assassinate the ruler of Saudi Arabia, U.S. officials said Thursday. The allegations are viewed as credible by U.S. authorities but investigators still are trying to determine if the plot was real and, if so, how far it advanced and whether Libyan leader Moammar Gadhafi was involved, according to two U.S. government officials. They spoke on condition of anonymity because of the sensitive nature of the case. The alleged plot against Saudi Crown Prince Abdullah...