Libyan leader Moammar Gadhafi is "the most dangerous" backer of the Irish Republican Army, which he has supplied with many advanced weapons and plastic explosives, a senior British leader said Thursday. Home Secretary Douglas Hurd also said Gadhafi has supplied the IRA with a plastic explosive called Semtex. British Transport Secretary Paul Channon has said the Czechoslovakian-made material was probably used in the bombing of the Pan American jumbo jet over Scotland last month in which 270 were killed. Authorities say they do not yet know who planted that bomb or why, and Hurd did not make any reference to the Pan Am disaster in his speech to a Rome military academy.