The United States has begun a blockade of the Strait of Hormuz, marking a sharp escalation in global maritime tensions that could disrupt one of the world’s most critical oil transit routes.

The announcement came despite a ceasefire agreed on last Wednesday to pause the six-week conflict between the United States and Iran until 22 April, with tensions centered on whether Washington can force Tehran to reopen the strategic waterway — one of its key demands in the stalled negotiations.

“The blockade will be enforced impartially against vessels of all nations entering or departing Iranian ports and coastal areas, including all Iranian ports on the Arabian Gulf and Gulf of Oman,” the US Central Command said in a statement, adding that it would begin at 10 p.m. on Monday.

The statement said US forces would not impede vessels transiting the Strait of Hormuz to and from non-Iranian ports, and that further instructions for mariners would be forthcoming.

The move immediately triggered concerns of supply shocks across Asia, including the Philippines, which relies heavily on imported oil transiting Middle East shipping lanes for its energy needs.

Analysts warned any sustained disruption in the strait could quickly translate into higher pump prices, inflationary pressure, and added strain on food and transport costs in the Philippines, while testing the resilience of regional shipping and insurance markets tied to Gulf-bound cargo routes.

Phl-Iran deal under scrutiny

Beyond global markets, the blockade is also casting uncertainty on a delicate diplomatic arrangement between Manila and Tehran, raising questions about whether the Philippines can sustain its hard-won energy security gains amid the escalating geopolitical tensions.

Just days before the latest blockade, the Philippines was able to secure assurances from Iran that guaranteed the safe and unimpeded passage of Philippine-flagged vessels and oil shipments through the vital waterway — an agreement seen as critical for a country that sources nearly all of its crude oil from the Middle East.

The deal, forged through quiet diplomacy, was designed to shield the country from supply disruptions and protect Filipino seafarers operating in one of the world’s most volatile oil corridors.

However, the US enforcement of a blockade — targeting vessels linked to Iranian ports — risks complicating that arrangement. While Washington has indicated it will not impede ships bound for non-Iranian destinations, the overlap of military enforcement and Iranian control introduces operational uncertainties for shipping lines, insurers, and fuel suppliers navigating the strait.

For the Philippines, the stakes are high.

The government had viewed its agreement with Iran as a “meaningful gain” in stabilizing supply flows during a period of global oil volatility. But with the two opposing powers now asserting control over the same strategic chokepoint, Manila may be forced to recalibrate its position — balancing its longstanding alliance with the United States against its pragmatic engagement with Iran to keep the fuel shipments coming.

Analysts warned that if the tensions persist, even ships granted safe passage by Tehran could face delays, higher insurance costs, or rerouting — factors that could quickly ripple into higher fuel prices and inflation in the Philippines.

U.S. to clear strait of mines

In a lengthy social media post, US President Donald Trump said his goal was to clear the strait of mines and reopen it to all shipping, and Iran must not be allowed to profit from its control of the waterway.

“Effective immediately, the United States Navy will begin the process of blockading ships trying to enter or leave the Strait of Hormuz,” Trump said, warning that any hostile action against US or commercial vessels would be met with force.

The speaker of Iran’s Parliament, Mohammad Bagher Ghalibaf, who led Tehran’s delegation in Pakistan, said upon returning home that the country would “not bow to any threats” from Washington, while Navy chief Shahram Irani called the blockade threat “ridiculous.”

Tehran has already been restricting traffic through the strait, while allowing some vessels serving friendly countries such as China to pass. There have been unconfirmed reports it plans to impose transit fees.