ISLAMABAD, April 13 -- President Donald Trump on Sunday said the U.S. Navy would "immediately" begin a blockade of ships entering or leaving the Strait of Hormuz, after US-Iran ceasefire talks in Pakistan ended without an agreement or next diplomatic steps in sight. In his first public comments after the 21-hour talks, Trump sought to eliminate Iran's key source of leverage in the war by exerting strategic control over the waterway that was responsible for the shipping of 20% of global oil supplies before fighting began. A US blockade could further rattle global energy markets. It was not immediately clear how it might be carried out, but Trump told Fox News the goal was to ensure all ships could transit: "It's going to be all or none, and ...