The US secretary of state said on Friday he was willing to travel to Iran for talks, as reports emerged that the regime had test-fired a medium-range missile.

Mike Pompeo, who has taken a hard line against Tehran as part of a US maximum-pressure policy, also challenged Boris Johnson to overturn his predecessor’s decision not to join a US operation to protect ships from Iranian attacks.

"Sure. If that's the call, I'd happily go there,” he told Bloomberg. “I would welcome the chance to speak directly to the people."

Tensions between Iran and the US have ratcheted up since last year, when President Donald Trump withdrew America from the nuclear deal, saying it was not strong enough.

Mr Trump and Iranian leaders have both publicly said talks were possible, but the prospect for dialogue appeared to recede on Wednesday when the top military adviser to Iran's Supreme Leader Ayatollah Ali Khamenei said Tehran would not negotiate with Washington under any circumstances.