US secretary of state Mike Pompeo has said Washington will designate a Yemeni rebel group a terrorist organisation on the Trump administration’s final day in office, despite widespread warnings that the move risks triggering a devastating famine in the impoverished Arab state.

Mr Pompeo said in a statement overnight that the designation of the Houthi movement, which is embroiled in an almost six-year civil war in Yemen, will take place on January 19 — one day before US president-elect Joe Biden is inaugurated.

The move would provide additional tools to confront terrorist activity and “advance efforts to achieve a peaceful, sovereign, and united Yemen that is both free from Iranian interference and at peace with its neighbours”, he said.

The US considers the Houthis an Iranian proxy and accuses Tehran of supplying the rebels with weapons, including missiles and drones to attack Saudi Arabia. But the UN and aid groups said labelling the movement — which controls Yemen’s populous north — a foreign terrorist group would have a severe impact on food imports into a country where an estimated 14m people, about half the population, are on the brink of starvation. The UN is leading diplomatic efforts to end the war.

Oxfam, the aid organisation, said the move would block US humanitarian aid, goods and personnel from entering northern Yemen, where 70 per cent of the population lives, and substantially reduce them throughout the rest of the country.

“Secretary Pompeo’s designation of the Houthis as a terrorist organisation is a counter-productive and dangerous policy that will put innocent lives at risk,” said Scott Paul at Oxfam. “Every day these designations remain in place will worsen the suffering of Yemen’s most vulnerable families.”

Mark Lowcock, UN under-secretary-general for humanitarian affairs, told the Financial Times last month that food imports to Yemen plummeted by a quarter in November amid speculation that Washington was planning to label the Houthis a terrorist organisation.

He added that importers and traders were worried about facing US sanctions if the designation went ahead.

“There’s a chilling effect of the [terrorist] designation . . . that risks undermining imports of food and becomes the final straw that tips the country into not just a small famine, but a large one,” Mr Lowcock said.

The Houthis, which seized Sana’a and forced the Yemeni government into exile in early 2015, control the capital and Hodeidah, a port city through which about two-thirds of the import-dependent nation’s goods are shipped. If the movement was labelled a terrorist group, any individual or organisation transacting with the Houthis would risk US sanctions.

Mr Pompeo, a hawk on Iran who is considered the driving force behind the move, said in a statement that the US “recognises concerns that these designations will have an impact on the humanitarian situation in Yemen”.

He said Washington was planning “to put in place measures to reduce their impact on certain humanitarian activity and imports into Yemen”.

But aid officials warn that the vast majority of food consumed in Yemen is imported by commercial traders.

Yemen has been devastated by conflict that has triggered what the UN describes as the world’s worst man-made humanitarian crisis.

More than 233,000 have died either through fighting or a lack of access to food and health services, since Saudi Arabia formed an Arab coalition to intervene in the war against the Houthis in March 2015.

Analysts and diplomats say that the Trump administration is going ahead with the move to make it more complicated for the incoming Biden administration to deal with crises in the Middle East.