A man looks at an International Red Cross flight dropping emergency food supplies in Leer, South Sudan.
Life-saving aid could move from Sudan to its former enemy South Sudan under a deal to feed some of the millions battling hunger in the war-torn South, a diplomat said on Wednesday.
The two countries signed a memorandum of understanding on Tuesday for the United Nations World Food Programme (WFP) to deliver food to northern South Sudan, said Kau Nak, the South's charge d'affaires in Khartoum.
"It's a kind of a life-saving mission," he told AFP on the third anniversary of the South's separation from Sudan.
More than 1.5 million people have been forced to flee almost seven months of war, after a power struggle between President Salva Kiir and his former deputy Riek Machar spiralled into brutal ethnic conflict that killed thousands.
Aid agencies have warned that without massive funding, famine zones will be declared within weeks.
The International Committee of the Red Cross has already been forced to air drop food in an effort to keep isolated groups of displaced people alive, calling it a "last resort" operation.
Plans call for WFP aid to be transported from Sudan to "the devastated Upper Nile, Jonglei and Unity states" in the South, according to a July 7 memo from South Sudan's ministry of humanitarian affairs and disaster management.
South Sudan separated from the north on July 9, 2011 after an overwhelming vote for independence under a peace deal that ended a 22-year civil war.
Ironically, tens of thousands of South Sudanese have fled into Sudan since the South's war began in December.
After independence, tensions persisted between north and south and led to border fighting in 2012.
Relations had begun to improve late last year, just before the South descended into what Oxfam, an aid group, calls Africa's worst crisis.
Sudan and South Sudan disagree over certain parts of their border, which has not been demarcated, while numerous pacts on economic and security issues have not taken effect.
Kau Nak said the aid deal is different.
"I don't see any difficulty of implementing it," he said, adding that he did not expect either country to retreat from its commitment.
- 'Worst famine' feared -
The memorandum calls for WFP aid to be sent by road and river from Sudan's Kosti town on the White Nile, north of South Sudan's Upper Nile state.
Sudan would provide security for the aid workers and cargo on its side of the border while the South would be responsible across the frontier, Kau Nak said.
"The two governments agreed to allow the humanitarian organisation to assist the affected population", he said.
Kau Nak signed the memorandum, on behalf of his country's humanitarian affairs ministry, with Sudan's Humanitarian Aid Commission.
HAC officials could not be reached.
Agreement on the "immediate passage" of the aid is "part of the government of Sudan commitment to facilitate delivery of humanitarian assistance to its neighbouring countries," the memorandum states.
Kau Nak did not have a figure for the number of people who could be helped under the initiative.
Nor does a written plan for the operation give a figure, but it projects that more than 66,000 tonnes of cereals, vegetable oil and other food would be moved by truck and barge over six months.
"Sudan is the nearest location in terms of logistics," Kau Nak said.
Oxfam said nearly four million people -- a third of South Sudan's population -- are in danger of severe hunger.
"We are at risk of seeing the worst famine in the country's history," South Sudan UN chief Hilde Johnson said Tuesday, ending her tour of duty.
She blamed the country's "self-serving elite" of leaders and rebels.