U.S. envoy Richard W. Murphy warned Iran against attacking American ships in the Persian Gulf, hours after the Iranians reportedly hit the third merchant ship in eight days in the gulf. "We regard any attack on an American ship as a very serious affair," Murphy, on a Mideast tour, said in Baghdad, Iraq. "We will do what is necessary to ensure the passage of our ships," he added. Earlier, an Indian tanker bound for Kuwait was hit by what was believed to be an Iranian patrol boat. Kuwait supports Iraq in its war with Iran.