U.S. President Donald Trump said Monday that the American military had begun a blockade of Iranian ports as part of his effort to force Tehran to open the Strait of Hormuz and accept a deal to end the war that has raged for more than six weeks.

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 the ceasefire 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. There has been no word on whether negotiations will resume.

Trump says the blockade has begun

In Washington, U.S. President Donald Trump said the blockade started at 10 a.m. EDT (2 p.m. GMT).

“We can’t let a country blackmail or extort the world because that’s what they’re doing,” Trump said of Iran.

Speaking outside the Oval Office, Trump suggested the U.S. is still willing to engage with Iran.

“I can tell you that we’ve been called by the other side,” Trump said.

He added: “We’ve been called this morning by the right people, the appropriate people, and they want to work a deal.”

Trump did not say who called or what was discussed.

Trump: “I can tell you we’ve been called by the other side. They’d like to make a deal very badly.”

Asked whether his earlier threats to destroy Iran’s critical civilian infrastructure still stands, Trump said: “I don’t want to comment on that, but it won’t be pleasant for them. Let me put it that way.”

Trump: “Iran will not have a nuclear weapon… If they don’t agree, there’s no deal. There’ll never be a deal. Iran will not have a nuclear weapon and we’re going to get the dust back either we’ll get it back from them or we’ll take it.”

Minutes before the scheduled start of the blockade, the United Kingdom Maritime Trade Operations agency issued a notice to mariners that said the restrictions included “the entirety of the Iranian coastline, including ports and energy infrastructure.”

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

Iran’s effective closure of the strait, through which 20% of traded oil passes in peacetime, has sent oil prices skyrocketing, pushing up the cost of gasoline, food and other basic goods far beyond the Middle East. Tehran has allowed some ships perceived as friendly to pass while charging considerable fees, leading to accusations it is holding the global economy hostage.

Some analysts are doubtful that the U.S. can restore normal shipping through force alone — and it’s not clear how a blockade would work or what the dangers might be to U.S. forces.

The question is essentially who can endure the most pain: Could a blockade make Iran’s economic situation untenable and force it to concede? Or will it drive global oil and other prices so high that Trump is forced to back down?

Blockade could have far-reaching effects

The U.S. military’s Central Command announced that the blockade would be enforced “against vessels of all nations entering or departing Iranian ports and coastal areas.” It said that would include all of Iran’s ports on the Persian Gulf and Gulf of Oman.

CENTCOM’s decision to allow ships traveling between non-Iranian ports to transit the strait was a step down from Trump’s earlier threat to blockade the waterway.

In a social media message posted shortly after the blockade was due to begin, Trump said Iran’s navy was “laying at the bottom of the sea, completely obliterated,” but he added that Tehran still has “fast attack ships,” and warned that “if any of these ships come anywhere close to our BLOCKADE, they will be immediately ELIMINATED.”

Iran issued threats of its own.

“Security in the Persian Gulf and the Sea of Oman is either for everyone or for NO ONE,” the Islamic Republic of Iran Broadcasting reported Monday. “NO PORT in the region will be safe,” read a statement from the Iranian military and the Revolutionary Guard.

The threats halted the limited ship traffic that resumed in the strait since the ceasefire, according to a report from Lloyd’s List Intelligence. Marine trackers say over 40 commercial ships have crossed since the start of the ceasefire last week, down from roughly 100 to 135 vessel passages per day before the war.

The blockade is likely intended to pile pressure on Iran, which has exported millions of barrels of oil since the war began, much of it likely carried by so-called dark transits that evade Western sanctions and oversight.

But the effects will be felt far beyond Iran. The price of Brent crude oil, the international standard, rose 7% to hover around $102 per barrel on Monday. It cost roughly $70 per barrel before the war.

British Prime Minister Keir Starmer said that, together with French President Emmanuel Macron, he would hold a summit this week “to drive forward the international effort” to end the conflict and unblock the strait.

On X, Macron said the conference will draw together nations prepared to contribute to a “peaceful multinational mission aimed at restoring freedom of navigation in the strait.” He stressed that the mission would be “strictly defensive” and “separate from the warring parties to the conflict.”

Iran says ‘if you fight, we will fight’

Top-ranking Iranian officials threatened retaliation.

Ebrahim Rezaei, a spokesperson for the Iranian parliament’s National Security Commission, dismissed U.S. warnings of a potential blockade as “more bluffing than reality,” while warning that Tehran was prepared to respond if the situation escalates militarily.

“It will make the current situation (Trump) is in more complicated and makes the market — which he is angry about — more turbulent. And we may also reveal other cards that we have not used in the game,” he said in a post on X.

The Iranian parliament speaker, Mohammad Bagher Qalibaf, addressed Trump in a statement: “If you fight, we will fight.”

Ceasefire holds after talks end without agreement

The blockade threat came after marathon U.S.-Iran ceasefire talks in Pakistan ended without an agreement on Saturday.

U.S. Vice President JD Vance said the talks stalled after Iran refused to accept American terms on refraining from developing a nuclear weapon.

Iran has insisted its nuclear program is peaceful. However, it has pushed forward with steps that could give it the ability to build a nuclear weapon, including enriching uranium to near weapons-grade levels and developing long-range missiles potentially capable of delivering a bomb.

Iran’s ambassador to India, Mohammad Fathali, said the main sticking points for Tehran were its nuclear program, war reparations and sanctions relief.

Neither Iran nor the U.S. has indicated what will happen after the ceasefire expires on April 22. The fighting has killed at least 3,000 people in Iran, 2,089 in Lebanon, 23 in Israel and more than a dozen in Gulf Arab states, and damaged infrastructure in half a dozen countries.

Pakistani Foreign Minister Ishaq Dar said his country will try to facilitate a new dialogue in the coming days.

Turkish Foreign Minister Hakan Fidan, whose country has supported mediation efforts, suggested that the ceasefire could be extended for 45 to 60 days to allow for more negotiations.

(AP)