India, April 14 -- The US military vowed to blockade all Iranian ports starting Monday in an effort to force Tehran to open the crucial Strait of Hormuz and accept a peace deal. Iran responded with threats on all ports in the Persian Gulf and the Gulf of Oman, taking aim at US-allied countries.

That set the stage for an extraordinary showdown that posed serious risks for the global economy and raised the specter that the ceasefire could collapse and the war could resume. Talks aimed at permanently ending the conflict - which began Feb. 28 with US and Israeli strikes on Iran - failed to reach an agreement this past weekend, and there has been no word on whether negotiations will resume.

It was not clear if the blockade had started when t...