As the US vice-president, JD Vance, took to a podium in Pakistan after 21 hours of diplomacy and said no deal had been reached to end the war with Iran, his boss Donald Trump was in Miami watching a mixed martial arts fight. The contrast was stark. Just when the outcome of a war and the stability of global markets hung in the balance, the president chose spectacle over engagement. Mr Trump may intend to project strength. But the impression he creates – in Tehran and among America’s allies – is of a president less interested in the substance of diplomacy than in the politics surrounding it.

The talks in Islamabad didn’t fail accidentally; the US and Iran were talking past each other. Washington’s position is that Iran must abandon its capacity to develop a nuclear weapon, while Tehran insists it is not seeking one and has the right to a civilian nuclear programme. The US........

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