ISLAMABAD (AP) – Afghanistan is seeing its sharpest-ever surge of child malnutrition, the World Food Program said Monday, adding it needed $539 million to help the country’s most vulnerable families.

Almost 10 million people, a quarter of Afghanistan’s population, face acute food insecurity. One in three children is stunted.

The WFP said the rise in child malnutrition was linked to a drop in emergency food assistance over the past two years because of dwindling donor support. In April, the U.S. government cut off food aid to Afghanistan, one of the world’s poorest countries.

The U.S. had been the largest funder of the WFP, providing $4.5 billion of the $9.8 billion in donations last year. Previous U.S. administrations viewed such aid as serving national security by alleviating conflict, poverty, extremism and curbing migration.

Food insecurity in Afghanistan is being worsened by mass returns from neighboring countries, which are deporting foreigners they say are living there illegally.

The WFP said it has supported 60,000 Afghans returning from Iran in the last two months, a fraction of those crossing the border.

“Going forward, the WFP does not have sufficient funding to cover the returnee response at this time and requires $15 million to assist all eligible returnees from Iran,” said WFP Communications Officer Ziauddin Safi. He said the agency needs $539 million through January to help vulnerable families across Afghanistan.

Climate issues are also hurting the population, especially those in rural areas.

Matiullah Khalis, head of the National Environmental Protection Agency, said last week that drought, water shortages, declining arable land, and flash floods were having a “profound impact” on people’s lives and the economy.