United Nations Secretary-General António Guterres on Tuesday warned of a looming “humanitarian catastrophe” in Afghanistan, calling on member countries to contribute aid to support Afghans in need.

Guterres said Tuesday that currently, “almost half of the population of Afghanistan — 18 million people — need humanitarian assistance to survive.”

The UN head said in a statement that Afghans face a “deepening humanitarian and economic crisis in the country” following the Taliban’s consolidation of power and as they conduct negotiations on the formation of a new government.

Concerns of access to aid have grown with the official departure of the U.S. military and other allied forces from Afghanistan, as well as fleeing aid workers.

“One in three Afghans do not know where their next meal will come from,” he continued. “More than half of all children under five are expected to become acutely malnourished in the next year. People are losing access to basic goods and services every day.”

“Now more than ever, Afghan children, women and men need the support and solidarity of the international community,” Guterres argued, adding that the “humanitarian system’s commitment to stay and deliver will not waver.”

The UN head noted that in the past year, the international organization had delivered aid to 8 million people, with food and relief packages brought to thousands of displaced families in the past two weeks.

However, Guterres said that “amid a severe drought and with harsh winter conditions on the horizon, extra food, shelter and health supplies must be urgently fast-tracked into the country.”

“I call on all parties to facilitate safe and unimpeded humanitarian access for life-saving and life-sustaining supplies, as well as for all humanitarian workers — men and women,” he said, adding that he planned to release next week more detailed recommendations on how to meet the immediate needs of Afghans.

“I urge all Member States to dig deep for the people of Afghanistan in their darkest hour of need,” he continued. “I urge them to provide timely, flexible and comprehensive funding. I urge them to help ensure humanitarian workers have the funding, access, and legal safeguards they need to stay and deliver.”

On Monday, the UN Security Council passed a resolution calling on the Taliban to not impose obstacles to the delivery of humanitarian assistance to the country.

It also urged the Taliban to allow for the safe passage of foreigners and Afghan civilians still hoping to leave the country, and also prevent terrorist groups from using Afghanistan as a safe haven.