The combined effects of war and drought linked to global warming have put one-third of Afghanistan's population - 14 million people - at risk of severe or acute hunger, the UN World Food Programme warned.
The dire assessment comes as the country faces an uncertain future after the Taliban routed the government to take power over the weekend.
"2021 is an extraordinarily difficult year for Afghanistan," WFP representative and country director Mary-Ellen McGroarty said in a telephone interview from Kabul.
Warning of a "horrendous humanitarian crisis unfolding", Ms McGroarty said she intended to remain in the south Asian nation with the WFP "to deliver the much needed humanitarian response that is now required".
The war-torn country is facing its second severe drought in three years, on top of the fighting and displacement of people, she said.
"We are in a dire situation, the latest analysis indicates that 14 million people are already at risk of severe or acute hunger," Ms McGroarty added, adding that two million children are at risk of malnutrition.
Wheat production has fallen 40% after one of the driest periods in almost 30 years.
"It's had a devastating impact as well on livestock," Ms McGroarty explained.
"As the conflict has escalated right across the country, farmers are unable to harvest the land, they're fleeing from their homes," she said.
Orchards have been destroyed in some areas, along with civilian infrastructure such as bridges, dams and roads.
"So, today, when you have the combined impact of the conflict with the drought, food is getting expensive."
The price of a bag of wheat is today 24% higher than the five-year average.
Ms McGroarty said it was a priority for the WFP to be able to stay and safely assist the Afghan population.
The UN's food-assistance arm negotiates to gain "unimpeded humanitarian access", she said.
"We don't take sides, we stay away from political discussions and stuff like that," Ms McGroarty said.
"We have a horrendous humanitarian crisis unfolding, it's essential that we're able to scale operations over the next couple of months."
The WFP hopes to reach nine million people in Afghanistan by the end of the year.
"In some of the areas where there are new authorities, the Taliban, we have resumed operations, but we need to be doing much, much more, we need to get out there."
The WFP has 480 staff right across Afghanistan, including 440 Afghan nationals.
"Winter is coming," she warned.
"We get severe winters in Afghanistan ... many communities are cut off ... so we need to get food stocks into those areas."