ISLAMABAD, April 15 -- The standoff between the United States and Iran deepened on Tuesday as the US declared it had blockaded Iran's ports, Tehran threatened to strike targets across the region, and Pakistan said it was racing to bring the sides together for more talks. Though last week's ceasefire appeared to hold, the showdown over the Strait of Hormuz risked reigniting hostilities and deepening the regional war's economic fallout. Talks aimed at permanently ending the conflict - which began February 28 with US and Israeli strikes on Iran - failed to produce an agreement last weekend, though Pakistan has proposed hosting a second round in the coming days. Two Pakistani officials, who spoke on condition of anonymity because they were not authorized to discuss the matter with the media, said that the first talks were part of an ongoing diplomatic process rather than a one-off effort. Two US officials said on Monday that discussions were still underway about a new round of talks. A diplomat from one of the mediating countries said that Tehran and Washington had agreed to it....