Iran's chief negotiator and parliament speaker Mohammad Bagher Ghalibaf warned on Sunday that Tehran would respond with greater speed and force to any further US military action, declaring that "the era of proportionate responses has come to an end." The warning follows a sharp escalation in a six-month conflict between the two countries, in which the US struck three Iranian oil tankers linked to the Islamic Revolutionary Guard Corps (IRGC) after Iran fired on two American warships — an aircraft carrier and a destroyer — in the region. The clashes are unfolding against the backdrop of a broader standoff over the Strait of Hormuz (the narrow waterway through which roughly one-fifth of global oil supplies pass), which Iran has blockaded while the US maintains counter-sanctions and a naval presence, with Washington insisting it will not resume negotiations until Iran halts attacks on commercial shipping.