Iran talks were a major test for JD Vance. How did he do?

US Vice-President JD Vance remained tight-lipped as he returned from Islamabad on Sunday without a major breakthrough in high-stakes talks to end the war in Iran.

It was unclear how much, if any, progress was made in the highest-level diplomatic negotiations between the US and Iran in decades.

After 21 hours of back and forth in the Pakistani capital, Washington and Tehran remain far apart on key sticking points, including Iran's nuclear programme.

The two sides did not reach an agreement on what to do with the regime's enriched uranium, said a US official, who offered new details on the talks on the condition of anonymity.

Other unresolved issues include reopening the Strait of Hormuz without toll charges, a top priority for President Donald Trump, and securing a commitment from Iran to stop funding proxy groups like Hezbollah and Hamas, the US official said.

Vance gave Tehran a final offer in the talks on Saturday, the US official said, without specifying details.

The meeting apparently wasn't entirely fruitless, however. The talks were tough but friendly and the two sides exchanged productive proposals, according to the US official.

Vance left Islamabad convinced that Iran was overplaying its hand, but still hopeful that a deal could be reached, said the US official.

Iranian President Masoud Pezeshkian said an agreement with the US "will certainly be found" if "the American government abandons its totalitarianism and respects the rights of the Iranian nation".

Trump made his displeasure with the lack of progress clear on Sunday.

The president said in social media posts on Sunday that the US would blockade the strait "effective immediately" to pressure Iran to reach a deal.

The US military said it would stop all maritime traffic entering and exiting Iranian ports from Monday morning.

Iran and the US agreed to a temporary two-week ceasefire last week, although Trump said in his latest Truth Social posts that "at an appropriate moment, we are fully 'LOCKED AND LOADED,' and our Military will finish up the little that is left of Iran".

Mohammad Bagher Ghalibaf, the speaker of Iran's parliament who led Tehran's delegation in Islamabad, sounded unfazed by Trump's sabre-rattling in a statement upon his return home.

According to reports by Iranian outlets, Ghalibaf addressed the US president, saying that "if you fight, we will fight, if you come forward with logic, we will respond with logic".

"We will not submit to any threat," he added. "If they test our resolve once more, we will teach them an even greater lesson."

The rhetoric underscores the massive gap between the two sides and the many remaining obstacles to reaching a full deal to end the war.

The negotiations represented a major test for 41-year-old Vance, who was picked by Trump to lead a US team that included special envoy Steve Witkoff and the president's son-in-law, Jared Kushner.

Vance landed in Islamabad on Friday tasked with finding a way to wind down what has become the biggest foreign policy crisis of Trump's second term.

The now six-week war has engulfed the Middle East and sent global oil prices soaring.

It was a difficult mission for Vance, negotiating on behalf of a president who has offered mixed messaging on the war from the start.

Trump joked in early April that he would blame the vice-president if talks fell through and take the credit if both sides struck a deal to end the war.

While Vance has backed the war in public, he has reportedly expressed scepticism of the military campaign in private meetings with Trump.

The vice-president has in the past positioned himself as an anti-interventionist, a view broadly popular with Trump's core Maga base.

The talks were watched closely for signs of how Vance might handle foreign policy in a potential 2028 run for the White House.

While Vance was leading the talks in Islamabad, Trump watched a UFC fight in Miami, Florida, alongside Secretary of State Marco Rubio, another rumoured 2028 contender and possible Vance rival.

Meanwhile, the clock is ticking.

And a breakthrough seems as elusive as ever, with the two-week truce deadline looming this month.

Follow the twists and turns of Trump's second term with North America correspondent Anthony Zurcher's weekly US Politics Unspun newsletter. Readers in the UK can sign up here. Those outside the UK can sign up here.