With top officials worrying out loud that Sudan is a "ticking time bomb" that could return to civil war, President Barack Obama and other leaders gathered on the fringes of the UN General Assembly last night to insist that the timetable for a referendum on possible secession for South Sudan is respected.
Declaring that the people of Sudan "need peace", Mr Obama said in an emotional address that "the fate of millions of people hangs in the balance. What happens in Sudan in the days ahead may decide whether people who have endured too much war, move towards peace or slip backwards to bloodshed."
He added: "What happens in Sudan matters to all of sub-Saharan Africa and it matters to the world."
Already semi-autonomous, South Sudan is meant to get the chance to vote on final secession from the rest of the largest country in Africa in a vote on 9 January next year. The holding of the referendum was a key provision of the 2005 peace treaty that ended two decades of civil war in Sudan.
Last night's unusual meeting, attended also by the leaders of Kenya, Rwanda, Uganda and Ethiopia as well as foreign ministers from an array of world powers, was convened amid growing concern that preparations for the referendum are lagging gravely behind.
Diplomats said that the purpose of the summit was plain: to impress upon Khartoum, which stands to lose access to about 80 per cent of the country's oil reserves in a divorce, that it must honour the promise to hold the referendum. Experts fear that otherwise a fresh war might be inevitable.
It was Hillary Clinton, the US Secretary of State, who termed Sudan a "time bomb". Ban Ki-moon, the UN Secretary General, has called it one of his "top priorities".
Not present at the meeting was Sudanese President Omar al-Bashir, who is wanted by the UN International Court on war crimes charges stemming from the violence in Darfur. He was represented instead by two vice-presidents: Ali Osman Taha, who speaks for the Khartoum government, and Salva Kiir who is the leader of South Sudan. Few doubt that a fair vote would result in the South, with its capital in Juba, opting to break away. If a "yes" vote does occur, the process of negotiating that break-up is likely to be lengthy and extremely difficult, not least because of the need to divide the oil reserves.
In a speech in New York this week, Mr Obama openly prodded Khartoum to do what it promises. "We will reach out to countries making the transition from authoritarianism to democracy, and from war to peace," the President said. "As others show the courage to put war behind them ... the United States will stand with those who seek to build and sustain peace."
Earlier this year, Dennis Blair, the US director of National Intelligence told Congress that South Sudan was the most likely place for "a new mass killing or genocide" within the next five years. The last civil war is estimated to have cost as many as two million lives.
Mr Kiir was in Washington last week lobbying the US to apply maximum pressure on Khartoum, warning that he considered the January date for the poll to be "sacrosanct" and that any slippage would cause violence on a "massive scale" in his country.