UN Secretary General Antonio Guterres will convene a high-level conference on aid for Afghanistan in Geneva on September 13.
“The conference will advocate for a swift scale-up in funding so the life-saving humanitarian operation can continue; and appeal for full and unimpeded humanitarian access to make sure Afghans continue to get the essential services they need,” said Mr Guterres's spokesman, Stephane Dujarric.
Afghanistan, now back under the control of the Taliban after 20 years of war, faces a “looming humanitarian catastrophe", Mr Dujarric said.
The UN said more than 18 million people in the country were in need of humanitarian assistance.
Mr Dujarric said development gains must also be protected and that the rights of women were an essential part of the country's future stability.
Afghanistan was heavily dependent on aid even before the Taliban regained power, with 40 per cent of the country's gross domestic product drawn from foreign funding.
About a third of the 38 million people in the country may not have a meal every day, Ramiz Alakbarov, the UN’s humanitarian chief in the country, told AP.
The UN’s World Food Programme has distributed food to tens of thousands of people in recent weeks, but with winter approaching and a drought continuing, at least $200 million is needed urgently to continue to feed the most vulnerable Afghans, he said.
“One in three Afghans do not know where their next meal will come from. Nearly half of all children under the age of 5 are predicted to be acutely malnourished in the next 12 months,” Mr Dujarric said.
On Thursday, the UN said it resumed humanitarian flights to parts of the country, linking the Pakistani capital Islamabad with Mazar-i-Sharif in northern Afghanistan and Kandahar in the south.
The EU has offered humanitarian aid to Afghanistan, but suspended a separate supply of development aid.
The country's main carrier, Ariana Afghan Airlines, resumed domestic flights on Friday, while the UAE has sent a plane carrying urgent medical and food aid, to assist thousands of Afghan families, especially the most vulnerable, such as women, children and the elderly.
Last week, the UAE hosted up to 8,500 Afghans at Emirates Humanitarian City in Abu Dhabi, where high-quality housing, sanitation, food and health care were provided by teams from several UAE entities.