International aid agencies say the five-year-old peace deal between north and south Sudan is facing collapse and there's a real risk of renewed civil war in Sudan unless the world acts now.
The report, by 10 agencies, blames a "lethal cocktail" of rising violence, chronic poverty and political tensions. A return to conflict would have devastating consequences extending far beyond south Sudan, they say.
The peace deal five years ago ended a 22-year civil war that left 1.5 million people dead.
It saw President Omar al-Bashir's northern National Congress Party (NCP) enter government with former Sudan People's Liberation Movement (SPLM) rebels from the south.
A key part of the deal was a referendum in January 2011, in which it is widely expected that the oil-rich south will vote for independence.
Heavy international presence a factor
The BBC's correspondent in the Sudanese capital, Khartoum, says the country is clearly at the start of a highly charged and risky 12 months; unlike at the outset of previous crises, however, there is a heavy international presence in the country.
The military worth of the UN peacekeeping mission has yet to be tested, but nearly 10,000 military personnel are charged with keeping the peace.
Sudan's ambassador to London, Omar Muhammad Siddiq, acknowledges that the situation in South Sudan is "deteriorating".
He says communities there are arming themselves and fighting "tribal wars", mainly over the competition for scarce resources.
Hopes that conflict can still be averted
British Foreign Office Minister Glenys Kinnock, who is due to visit Sudan, says it's one of the world's poorest countries.
"They are doing disastrously," she says, "and that is reflected in the terrible poverty and relentless suffering of the people."
But she believes that full-blown conflict could still be averted. "I think we still have time to ensure that we do see a peaceful, stable Sudan being built around the framework of an election and a referendum," she says.