United Nations chief Antonio Guterres voiced concern Wednesday over "escalation" in Sudan's conflict to the country's army chief when they met on the sidelines of a diplomatic gathering in New York.
Sudan has been high on the agenda at the UN's centerpiece meeting this week, with the dire humanitarian situation and refugee crisis dominating discussions on the war that broke out in April last year.
The conflict between two rival generals -- the head of the army, and the head of the paramilitary Rapid Support Forces (RSF) -- has so far displaced more than 10 million people, a fifth of Sudan's population, both within the country and across borders.
"People in Sudan have endured 17 months of hell, and the suffering continues to grow," said the UN's top relief official Joyce Msuya.
A UN-backed assessment has warned of the risk of widespread famine in Sudan on a scale not seen anywhere in the world in decades.
"The secretary-general expressed deep concern about the escalation of the conflict in the Sudan, which continues to have a devastating impact on the Sudanese civilians and risks a regional spillover," said a UN readout of Guterres's meeting with General Abdel-Fattah Al-Burhan.
The United States, European Union, France and Germany in a joint statement after talks among their ministers urged an immediate ceasefire and negotiations, and voiced alarm over foreign interference.
All foreign powers should "refrain from providing military support to the warring parties," they said after broader talks that included the United Arab Emirates, widely considered the top backer of the RSF.
- 'Apocalyptic' conditions -
The United States earlier Wednesday announced $424 million in new aid for displaced and hungry Sudanese as it urged others to ramp up efforts for one of the world's worst humanitarian crises.
The assistance includes $175 million with which the US will buy some 81,000 metric tons of surplus food from its own farmers to feed people in and around Sudan, American officials said.
Linda Thomas-Greenfield, the US ambassador to the United Nations, told a UN event that the world must scale up its efforts "massively" as she regretted that many were ignoring "a catastrophe of truly unfathomable proportions."
"As we sit here today, more than 25 million Sudanese face acute hunger. Many are in famine, some reduced to eating leaves and dirt to stave off hunger pangs -- but not starvation," she said.
"This humanitarian catastrophe is a man-made one -- brought on by a senseless war that has wrought unspeakable violence and by heartless blockades of food, water and medicine for those made victims of it," Thomas-Greenfield said.
"The rape and torture, ethnic cleansing, weaponization of hunger -- it is utterly unconscionable," she said.
She made a new appeal to let assistance into El-Fasher, which has been besieged by the RSF as the paramilitary force seeks a complete takeover of the western Darfur region.
The UN's refugees chief Filippo Grandi warned Wednesday that "conditions are apocalyptic" in Sudan.
"If people don't die because of bullets, they starve to death. If they manage to survive, they must face disease or floods or the threat of sexual violence and other horrifying abuse, which if perpetrated in other places would make daily headlines," he said.
The World Health Organization said this month at least 20,000 people have been killed. But some estimates are far higher, with the US envoy for Sudan, Tom Perriello, saying that up to 150,000 people may have died -- far more than in the war in Gaza.