ABOARD USS GEORGE H.W. BUSH - A US aircraft carrier passed through a strategic waterway separating Iran from US-backed Arab states on Tuesday for the first time since President Donald Trump took office two months ago.Nearly 20 smaller Iranian boats looked on as the USS George H.W. Bush approached the Gulf through the Strait of Hormuz. About one-fifth of the world's oil passes through the Strait and there are occasional incidents in the area involving US and Iranian military vessels.Years of mutual animosity eased when Washington lifted sanctions on Tehran last year after a deal to curb Iran's nuclear goals. But serious differences remain over Iran's ballistic missiles as well as conflicts in Syria and Iraq.While still a presidential candidate in September, Trump vowed that any Iranian vessels that harassed the US Navy in the Gulf would be "shot out of the water."