US military is poised to blockade Iranian ports, while Tehran threatens ports in the Mideast

The U.S. military vowed to blockade all Iranian ports starting yesterday, part of efforts to force Tehran into agreeing to open the crucial Strait of Hormuz and accepting a peace deal. Iran responded with threats on all ports in the Persian Gulf and the Gulf of Oman, taking aim at U.S.-allied countries.

That set the stage for an extraordinary showdown that posed serious risks for the global economy and raised the specter that a ceasefire that is currently holding could collapse and the war could resume. Talks aimed at permanently ending the conflict — which began Feb. 28 with U.S. 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 the designated time of 10 a.m. EDT (2 p.m. GMT) arrived. Minutes earlier, a notice to mariners issued by the United Kingdom Maritime Trade Operations agency, which monitors maritime security, said the restrictions included “the entirety of the Iranian coastline, including ports and energy infrastructure.”

The notice added that transit through the strait “to or from non-Iranian destinations is not reported to be impeded by these measures,” but it added that ships “may encounter military presence” in the strait.