Even on its final day in office, the Trump administration intends to unleash a thunderbolt in the Middle East that will imperil the lives of millions. Mike Pompeo, the US secretary of state, last week announced that Washington would designate the Houthi rebel movement in Yemen a foreign terrorist organisation the day before Joe Biden’s inauguration. The UN and other experts have warned that the move risks tipping the country into a famine on a scale not witnessed since the 1980s catastrophe in Ethiopia.

Mr Pompeo said the designation would provide “tools” to counter terrorist activity and “advance efforts” to achieve a peaceful and united Yemen. But it is an irresponsible act that will complicate UN efforts to broker a resolution to Yemen’s war and deepen the suffering of millions in a nation devastated by nearly six years of conflict.

The timing of the designation is no coincidence. Rather, it seems part of a cynical effort to scupper Mr Biden’s ability to ease Middle East crises and reset US policy. In addition, Mr Pompeo no doubt has an eye on his own political future and a self-serving desire to make Mr Biden appear weak on Iran, which supports the Houthis.

It is not the only foreign policy grenade the Trump administration has lobbed during the tumultuous US transition. After losing November’s election, President Donald Trump upset years of US policy by recognising Morocco’s sovereignty claim over the disputed territory of Western Sahara. That was part of a blatantly transactional deal under which Rabat agreed to normalise ties with Israel. This month, Mr Pompeo declared Cuba a state sponsor of terrorism, and lifted longstanding restrictions that limit US diplomatic relations with Taiwan, which will infuriate Beijing just as Mr Biden settles into the White House.

But it is Yemen where the Trump administration’s final acts are likely to have the most immediate and devastating consequences. The country has been at war since the Houthis seized Sana’a, the capital, and forced the government into exile in early 2015. Saudi Arabia then formed an Arab coalition to fight the rebels. The result is a calamitous conflict in which all parties may have committed war crimes, according to UN expert panels.

The Houthis recruit child soldiers, hamper aid agencies’ work and attack Saudi Arabia with missiles and drones that Riyadh and Washington claim are supplied by Iran. But the designation is likely to push them closer to Tehran and risks hardening the stances of both the Houthis and the Saudi-backed government.

The humanitarian consequences could be horrific. The UN warns the move will choke food flows into the import-dependent country and complicate aid agencies’ life-saving work. Traders, who import nearly all Yemen’s food, worry that bankers, shippers and insurers will refuse to do business with them for fear of US sanctions.

The Houthis control the populous north and the main port of Hodeidah. There are reports of panic buying as concerns grow that prices will rocket, pushing food costs further beyond most people’s means. The UN says some 16m Yemenis already go hungry and 50,000 “are essentially starving to death”.

Mr Biden must make reversing the designation a priority and end his predecessor’s dangerous folly. The best way to negate the Houthi threat and relieve Yemenis’ suffering is to throw US weight behind diplomatic efforts to convince all the protagonists to halt the fighting and reach a political settlement. Imposing a collective punishment on a shattered nation and triggering famine would be disastrous for all.