More than half the population of South Sudan are facing food shortages due to the continuing conflict with Sudan, the UN is warning.
It says fighting on the border between the two countries and the shutdown of oil production have had a devastating impact on the South's economy.
It adds there are fears the situation in the South, which gained independence from Sudan last July, is worsening.
Previous estimates suggest 4.7 million people are at risk of food shortages.
In this latest report, the UN Office for the Coordination of Humanitarian Affairs (Ocha) says a complex combination of factors has "raised fears that the South Sudanese are sliding into destitution".
Those factors include:
- clashes between north and south along the contested border regions
- inter-communal violence in Jonglei state
- the closure of oil production in a row over transit fees with Khartoum.
Citing research from the World Food Programme, the report says food shortfalls have continued to worsen in the first four months of 2012. It says at least one million people will be food insecure this year while a further 3.7 million people are borderline.
Refugee burden It says the country is looking at a deficit of cereal crops of nearly half a million tons - the worst in peacetime and more than twice last year's shortfall.
It also says that poor infrastructure makes the delivery of humanitarian aid extremely precarious.
The continued arrival of southern refugees who had been living in the north is also placing a further burden on this fragile new country, says the BBC's Richard Hamilton.
Earlier this month rebels from the former rebel Sudan People's Liberation Movement (PSALM)-North described the plight of the civilian population in Blue Nile state - just north of the border - as catastrophic and said that more than 200,000 people were in dire need of food.
Adding to the cataclysmic predictions, our correspondent says, a leaked briefing from the World Bank talked of South Sudan's economy as teetering on the brink of collapse - although it later retracted those remarks, saying they had been taken out of context.
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