The United Nations warned on Friday that it had only received 12 percent of the $2.7 billion being sought for war-wracked Sudan, adding that "famine is closing in".
Tens of thousands of people have died and millions have been displaced in Sudan since war broke out in April 2023 between the army and the Rapid Support Forces (RSF).
The United Nations says more than 1.4 million people have fled the country.
"It is a catastrophically underfunded appeal," Jens Laerke, spokesman for the Office for the Coordination of Humanitarian Affairs (OCHA) told reporters.
"Without more resources coming in fast, humanitarian organisations won’t be able to scale up in time to stave off famine and prevent further deprivation," he said, AFP reported.
"In Sudan, half of the population, 25 million people, need humanitarian aid. Famine is closing in. Diseases are closing in. The fighting is closing in on civilians, especially in Darfur."
The United Nations has expressed growing concern in recent days over reports of heavy fighting in densely populated areas as the RSF seeks control of El-Fasher, the last major city in the western Darfur region not under its control.
"Now is the time for donors to make good on pledges made, step up and help us help Sudan and be part of changing the current trajectory that's leading toward the cliff's edge. Don't be missing in action," he said.
Shible Sahbani, the UN's World Health Organization representative in Sudan, said: "Thirteen months of war in Sudan, nine million people displaced which represent around 17 percent of the population and the largest internal displacement crisis in the world today.
"This conflict has... nearly destroyed the health system which is almost collapsed now. Close to 16,000 people have died due to this war, 33,000 have been injured," she said, speaking from Port Sudan.
Sahbani said the real toll was "probably much higher".
The RSF and Sudan's armed forces are seen as both wanting to secure a battleground victory and each side has received support from outside players.
The UN human rights chief Volker Turk this week separately spoke to Lieutenant-General Abdel Fattah Al-Burhan, president of the Transitional Sovereignty Council, and General Mohamed Hamdan Dagalo, Commander of the Rapid Support Forces.
"He urged them both to act immediately – and publicly – to de-escalate the situation," UN human rights spokeswoman Ravina Shamdasani said.
