People displaced from Khartoum receive food assistance in Wad Medani, Aj Jazirah State. Photo courtesy of United Nations Office for the Coordination of Humanitarian Affairs (OCHA).
But assistance to even those four million could soon stop, Clementine Nkweta-Salami told AFP in an interview, if the chronic lack of funding continues.
The UN's humanitarian Coordinator for Sudan says eight months into a conflict between rival generals that has torn the country apart, the situation is "catastrophic".
Aid workers have called it the "forgotten war".
On April 15, army chief Abdel Fattah al-Burhan and his former deputy Mohamed Hamdan Daglo, who commands the paramilitary Rapid Support Forces, turned their weapons on each other.
Two years after the former allies co-engineered a 2021 military takeover sidelining civilians from power, their forces have killed more than 12,190 people in their brutal struggle for power, according to the Armed Conflict Location & Event Data Project (ACLED).
That figure is only a conservative estimate, however, with entire parts of the country completely cut off from the world.
There are also "seven million people displaced in Sudan, which is the highest displacement situation globally," Nkweta-Salami said.
Yet despite the scale of the crisis, the humanitarian response remains woefully underfunded.
"We've received only 38.6 percent" of the total $2.6 billion needed for 2023, Nkweta-Salami said.
"There will come a time when even if we have (physical) access, we will not have the resources to enable us to channel the relevant assistance that we need to do," she warned.
Sudan, whose tragedy has been overshadowed by the Israeli war on Gaza, saw nearly all aid groups disappear soon after fighting broke out, their warehouses looted and workers harassed or attacked.
"I have never, in all my years, seen such a horrific mega-catastrophe with so little attention or resources to reach people in their hour of greatest need," said Jan Egeland, secretary general of the Norwegian Refugee Council, one of a handful of organisations still providing vital aid across Sudan.
"Millions are trapped in the crossfire, in ethnic violence, in bombardments, and we are simply not there," he told AFP.
The gaps, Egeland and Nkweta-Salami agree, are huge.
According to the UN representative, "we are facing a population that is about 24.7 million people in need of humanitarian assistance," or more than one in two Sudanese.
"To date, we've been able to reach about four million and our goal is to hopefully reach around 18 million" who face immense challenges with "health, water and sanitation, food and malnutrition," she continued.
Only recently was the UN able to regain limited access through Chad into areas of Darfur, Sudan's vast western region where the UN has warned of "genocide".