U.S., AT U.N., CLAIMS SELF-DEFENSE FOR GULF ATTACK The United States invoked the right of self-defense in destroying an Iranian oil platform in the Gulf, the American delegation told the United Nations. Lieutenant General Vernon Walters sent letters about the incident to Security Council President Maurizio Bucci, the delegate of Italy, and Secretary General Javier Perez de Cuellar. U.N. press secretary Francois Giuliani said the Secretary General had no comment on the attack, which followed his appeal last Friday for restraint in the crisis while he pursued efforts to obtain a ceasefire between Iran and Iraq. In his explanation, Walters said the United States took defensive action in response to an Iranian attack against American ships in the Gulf. He cited an Iranian Silkworm missile strike last Friday in Kuwait waters against the United States-flag ship Sea Isle City. Walters said that military forces on the destroyed Iranian platform had engaged in a variety of actions against United States-flag and other nonbelligerent vessels and planes. "In accordance with Article 51 of the United Nations (Charter), I wish, on behalf of my government, to report that United States forces have exercised the inherent right of self-defense under internation law by taking defensive action in response to attacks by . . . Iran against United States vessels in the Gulf," Walters said. Members of the Security Council met behind closed doors on Monday to discuss developments in the Gulf war, but no statement was issued afterwards.