In a new chapter of the increasingly intertwined relationship between Iran and the US, Washington has sent more warships to the coast of Yemen to intersect potential shipments of Iranian arms.

The US has accused Tehran of supporting the Houthis with weapons and training, and has supported the campaign of air strikes by Saudi Arabia and a coalition of Sunni Arab governments that began in March.

Washington has reportedly been providing Riyadh with logistical and intelligence support, and has begun refuelling coalition aircraft carrying out the strikes.

The US’ increasing involvement in the Yemen conflict could find it sucked into a potentially long and gruelling war in one of the region’s most fractured countries.

This show of force against Iran comes as Iranian and American leaders are on the cusp of reaching a breakthrough on Tehran’s controversial nuclear programme.

At a time when US-Iran relations appear at their closest for decades, the two countries find themselves on either side of what has been painted as an Iran-Saudi proxy war.

Some analysts see the US assistance in Yemen as a way of signalling to its main allies in the region – including Saudi Arabia, Egypt and Israel – that it is willing to check Iranian influence even if a nuclear deal is signed.

The US has been working on the same side as the Islamic Republic to counter the spread of the jihadist group Islamic State in Iraq and Syria (Isis) in Iraq, but says they have not cooperated in any military operations.

US government officials have downplayed the idea that the escalating conflict in Yemen could derail the nuclear talks, pointing out that Iran has opposed US interests in the Syrian civil war for several years.

Washington and its allies will hope a successful nuclear agreement will lead to the emergence of a more moderate, diplomatic Iran, more focused on economic growth and development than using its influence in regional conflicts.

Tehran itself denies supporting the Houthis and is unlikely to show its support for the rebels with such high stakes riding on the outcome of the nuclear negotiations.