The UN has blamed the Sudanese government and rebels for blocking all humanitarian aid where more than 900 000 people need help.
The director of the United Nations' humanitarian operations John Ging said a year-long effort to get access to South Kordofan and Blue Nile states has failed because of a lack of "political will" by the government and the rebels who are allied with guerrilla forces that eventually came to power in South Sudan.
"The humanitarian status of these people is truly appalling," Ging told reporters after briefing the Security Council.
"If we don't find a solution to this, then the inevitable consequence is more people will die, more needless humanitarian suffering will occur and more displacement into South Sudan and Ethiopia."
The fighting in South Kordofan and Blue Nile, which Ging said is intensifying, pits the Khartoum government against rebels from the Sudan People's Liberation Movement-North, or SPLM-N, who were left on the north's side of the border in Sudan after South Sudan became independent in July 2011.
The separation followed a peaceful independence vote guaranteed in a 2005 peace deal that ended decades of civil war. After fighting in South Kordofan and Blue Nile began in 2011, access to the remote region by the United Nations and international aid agencies was restricted and then banned by the Sudanese government, making it difficult to verify conditions in the area.
Ging said a year-long effort by the UN, Arab League and African Union to get the government and SPLM-N to agree to humanitarian access to the two states failed and the situation is dire and urgent.
He said he urged the Security Council to move from rhetoric to action and implement a resolution it adopted in May 2012 calling for the two parties to allow humanitarian workers and aid into the two states.
Currently, Ging said, over 900 000 people are in a "truly appalling" state, including 450 000 in South Kordofan, 230 000 in Blue Nile and 205 000 who have fled to South Sudan and Ethiopia.
"We receive them as refugees, hear their stories, see their physical state," he said. "When we see them, it's obvious to us that there is a severe humanitarian crisis in these two places."
"We hear incredibly alarming stories about people having to rely on roots and leaves. ... People are dying in South Kordofan, that is what we are being told. And [when] we look at the emaciated state of children and adults who have successfully made the journey out of these two areas, we can see in their physical state the obvious suffering that they have endured for a very long time."
US Ambassador Susan Rice said there is blame on both sides, "but the preponderance is and has been on the government in Khartoum".
"We urge the two parties to conduct urgent talks on humanitarian access, a cease-fire, and a political resolution of their conflict," she said.
Sudan's UN Ambassador Daffa-Alla Elhag Ali Osman countered that the deteriorating situation in rebel-controlled areas "is caused by the rebels themselves because they escalate the military actions, not only in the areas they control but even in the areas inhabited by civilians in the other parts".
He accused the government of South Sudan of supplying the SPLM-N rebels with military equipment and logistical support - an allegation that South Sudan's President Salva Kiir denies - and demanded that South Sudan stop all backing for the rebels.
Osman stressed that his government "has the political will to settle all disputes with the government of South Sudan".
The leaders of Sudan and South Sudan met in Addis Ababa, Ethiopia on Saturday and agreed to the unconditional and speedy implementation of deals reached in September to demilitarise their shared borders and allow oil exports to flow from South Sudan's oil fields north through Sudan's pipelines.
The issue of humanitarian access to South Kordofan and Blue Nile was not on the agenda. – Sapa-AP