ISLAMABAD (AP) — President Donald Trump on Sunday said the U.S. Navy would “immediately” begin a blockade to stop ships from entering or leaving the Strait of Hormuz, after historic U.S.-Iran ceasefire talks in Pakistan ended without an agreement or next diplomatic steps in sight.

In his first public comments after the 21-hour talks, Trump sought to exert strategic control over the waterway that was responsible for the shipping of 20% of global oil supplies before the war, hoping to eliminate Iran’s key source of leverage.

A U.S. blockade could further rattle global energy markets and prices for oil, natural gas and related products. It was not immediately clear how it might be carried out, but Trump told Fox News the goal was to ensure all ships could transit: “It’s going to be all or none, and that’s the way it is.”

Trump said he has “instructed our Navy to seek and interdict every vessel in International Waters that has paid a toll to Iran. No one who pays an illegal toll will have safe passage on the high seas.” Other nations would be involved in the blockade, he said, but did not name them.

During the talks, the U.S. military said two destroyers transited the strait ahead of mine-clearing work, a first since the war began. Iran’s state media said the joint military command denied that.

Trump stressed that Tehran’s nuclear ambitions were at the core of the failure to end the war, and the U.S. was ready to “finish up” Iran at the “appropriate moment." In comments to Fox News, he again threatened to strike civilian infrastructure and said he was fine with his widely criticized threat shortly before the ceasefire announcement that a “whole civilization will die tonight.”

No word on what happens after ceasefire expires

The face-to-face talks that ended earlier Sunday were the highest-level negotiations between the longtime rivals since the 1979 Islamic Revolution. Both delegations later left Islamabad.

Neither indicated what will happen after the 14-day ceasefire expires on April 22. Pakistani mediators urged all parties to maintain it. Each side said their positions were clear and blamed the other.

“We need to see an affirmative commitment that they will not seek a nuclear weapon, and they will not seek the tools that would enable them to quickly achieve a nuclear weapon,” Vice President JD Vance, leading the U.S. side, said afterward.

Iran’s parliament speaker Mohammad Bagher Qalibaf, who led Iran's side, said it was time for the United States “to decide whether it can gain our trust or not.” Iranian officials earlier said talks fell apart over two or three key issues, blaming what they called U.S. overreach.

Pakistani Foreign Minister Ishaq Dar said his country will try to facilitate a new dialogue in the coming days. Iran said it was open to continuing the dialogue, Iran’s state-run IRNA news agency reported.

The European Union urged further diplomatic efforts. The foreign minister of Oman, on the Strait of Hormuz' southern coast, called for parties to “make painful concessions." And the Kremlin said Russian President Vladimir Putin “emphasized his readiness” to help bring about a diplomatic settlement in a call with Iran's president.

Iran's nuclear program is a key sticking point

Iran’s nuclear program had been at the center of tensions long before the U.S. and Israel launched the war on Feb. 28. The fighting has killed at least 3,000 people in Iran, 2,020 in Lebanon, 23 in Israel and more than a dozen in Gulf Arab states, and caused lasting damage to infrastructure in half a dozen Middle Eastern countries.

Tehran has long denied seeking nuclear weapons but insisted on its right to a civilian nuclear program. The landmark 2015 nuclear deal took well over a year of negotiations. Experts say Iran's stockpile of enriched uranium, though not weapons-grade, is only a short technical step away.

An Iranian diplomatic official, speaking on condition of anonymity because of the sensitivity of closed-door talks, denied that negotiations had failed over Iran's nuclear ambitions. “Iran is not seeking to acquire nuclear weapons, but it has the right to nuclear energy for peaceful purposes,” the official said.

Inside Iran, there was fresh exhaustion and anger after months of unrest that had begun with nationwide protests against economic issues and then political ones, and then weeks of sheltering from U.S. and Israeli bombardment.

“We have never sought war. But if they try to win what they failed to win on the battlefield through talks, that’s absolutely unacceptable,” 60-year-old Mohammad Bagher Karami said in Tehran.

More questions as Israel presses ahead in Lebanon

Iran’s 10-point proposal for the talks had called for a guaranteed end to the war, including the end of fighting against Iran’s “regional allies,” explicitly calling for a halt to Israeli strikes on the Iranian-backed Hezbollah in Lebanon.

Israel has said the ceasefire deal did not apply in Lebanon, but Iran and Pakistan said otherwise. Negotiations between Israel and Lebanon are expected to begin Tuesday in Washington after Israel’s surprise announcement authorizing talks despite their lack of official relations.

The day the Iran ceasefire deal was announced, Israel pounded Beirut with airstrikes, killing more than 300 people in the deadliest day in Lebanon since the war began, according to the country’s Health Ministry.

Though Israel’s strikes have calmed in Beirut, its attacks on southern Lebanon have intensified alongside the ground invasion it renewed after Hezbollah launched rockets toward Israel in the war's opening days.

Lebanon’s state-run National News Agency reported six people were killed Sunday by a strike in Maaroub village near the coastal city of Tyre.

Israel wants Lebanon's government to assume responsibility for disarming Hezbollah, but the militant group has survived efforts to curb its strength for decades.

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Metz reported from Ramallah, West Bank, Boak from Miami and Magdy from Cairo. E. Eduardo Castillo in Beijing, Collin Binkley and Ben Finley in Washington, Kareem Chehayeb in Beirut and Ghaya Ben MBarek in Tunis contributed.