UN agencies said there would be an increase in food shortages in parts of Yemen in the next six months, mainly because of the overall economic decline and the Covid-19 pandemic that has ripped through the Arab world's poorest country.
A report by the World Food Programme, the UN children's fund and the Food and Agriculture Organisation said the number of people facing high levels of acute food insecurity was expected to increase from two million to 3.2 million in southern Yemen.
The country is facing the worst food crisis in the world, mostly because of the war started in 2014 when the Iran-backed Houthi rebels seized the capital Sanaa.
Economic shocks, conflict, floods, desert locusts and now Covid-19 are creating a perfect storm that could reverse hard-earned food security gains in Yemen, the report said.
"Yemen is facing a crisis on multiple fronts," said Laurent Bukera, the WFP director for Yemen. "We must act now. In 2019, thanks to a massive scale-up, WFP and partners were able to reverse the deterioration in the worst-hit areas of Yemen."
Yemen's conflict has killed more than 100,000 people and created the world's worst humanitarian disaster, with more than three million people internally displaced and two-thirds of the population reliant on food assistance for survival.
Donor countries recently cut back on aid to Yemen because of the effects of the pandemic and concerns that the aid might not be reaching its intended recipients in territories controlled by the Houthis.
"Yemen is again on the brink of a major food security crisis. ... unless we receive the funding we need now, we won't be able to do the same this time," said Lise Grande, UN humanitarian co-ordinator for Yemen.
She said the UN agencies faced a similar situation 18 months ago but generous funding prevented a famine.
About 24 million Yemenis, 80 per cent of the country's population, require some form of assistance or protection, according to the UN Office for the Co-ordination of Humanitarian Affairs.
Seventy-five per cent of UN programmes for the country, covering essentially every sector, from food to health care and nutrition, have already shut down or reduced operations.