Iran Reasserts Control, Closes Strait of Hormuz Amid U.S. Threats

Iran's Islamic Revolutionary Guard Corps (IRGC) Navy declared the Strait of Hormuz closed on Saturday, April 18, 2026, warning that any vessel attempting passage would be targeted. The announcement came less than 24 hours after the waterway had been briefly reopened, reigniting concerns over maritime security in the Persian Gulf and the broader U.S.-Iran standoff.

The IRGC statement, relayed by Iran's Student News Agency, stipulated that the closure would remain in effect until the United States lifts its naval blockade on Iranian vessels and ports—a move Tehran labels a breach of the cease‑fire agreement linked to the ongoing U.S.-Israel conflict with Iran.

Speaker of Iran's Parliament Mohammad Bagher Ghalibaf emphasized on television that “the Strait of Hormuz is under the control of the Islamic Republic,” condemning the U.S. blockade as “clumsy and ignorant.” Meanwhile, Supreme Leader Mojtaba Khamenei warned the navy was prepared to deliver “new bitter defeats” to its adversaries.

Just hours earlier, Iranian Foreign Minister Abbas Araghchi had announced the strait “completely open for all commercial vessels,” prompting a brief surge of more than a dozen merchant ships and a dip in global oil prices. The sudden reversal underscores the volatility of the region’s energy markets, where even short‑lived openings can sway price benchmarks.

According to the United Kingdom Maritime Trade Operations (UKMTO), Iranian gunboats fired on two commercial vessels, and India’s Ministry of External Affairs confirmed that two Indian‑flagged ships were involved in a “shooting incident.” Some merchant crews reported receiving radio warnings from the IRGC Navy that no ships would be permitted through the strait.

U.S. President Donald Trump responded by stating Tehran could not “blackmail Washington” and warned that the naval blockade would “remain in full force” unless a cease‑fire deal is secured before its Wednesday deadline. Trump also hinted at ending the cease‑fire if Iran persists with the closure.

Al Jazeera analysts described the situation as “two competing blockades,” noting that the brief reopening had raised hopes for a confidence‑building measure, only to revert to a stalemate. Correspondent Zein Basravi observed that the strait has become “the only space for engagement,” even if that engagement is hostile, serving as a platform for Iran to signal leverage to the United States.