Barack Obama presses for peaceful Sudan referendum
US President Barack Obama has told a special UN meeting that a referendum on Sudan's future must go ahead peacefully and on time.
Southern Sudanese are due to vote in January on whether they want the semi-autonomous region to become independent.
But preparations for the elections are behind schedule, with authorities not even having decided who is to vote.
Southerners insist that the referendum be held on time, and not postponed.
"At this moment the fate of millions of people hangs in the balance," Mr Obama told the UN meeting.
"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: "The comprehensive peace agreement that ended the civil war must be fully implemented. The referenda on self determination scheduled for January 9 must take place, peacefully and on time."
The referendum was part of a 2005 peace deal to end two decades of conflict between the north and oil-rich south, but observers fear delays or the lack of a credible vote could spark fresh conflict.
Sudanese President Omar Bashir has repeatedly said the vote will be free and fair, but critics are not convinced, and some accuse him of deliberately dragging his heels.
Mr Bashir, who is wanted at the International Criminal Court for alleged war crimes over the separate conflict in Darfur, is being represented by his vice-president Ali Osman Taha, while Southern Sudan is being represented by its leader, Salva Kiir.
Following Mr Obama's speech, Mr Ali Osman Taha said Khartoum would accept the result of the referendum but it wants international sanctions eased.
He also condemned the international warrant for the arrest of Mr Bashir.
Earlier this month, US Secretary of State Hillary Clinton called the 9 January vote a "ticking time bomb", saying that an outcome in favour of succession was "inevitable".
She expressed concern that the north was unlikely to welcome the prospect of losing its share of oil revenues and that the south should make "some accommodations" for it, to prevent a return to conflict.
Southern Sudan, where most people are Christian or follow traditional religions, is already semi-autonomous and is run by the SPLA former rebels, who fought the Muslim-dominated, Arabic-speaking north until the 2005 deal.
In another development on Friday, the African Union urged the UN Security Council to delay the prosecution of Mr Bashir for a year to avoid destabilising Sudan.
Addressing the UN General Assembly, AU chairman President Bingu wa Mutharika of Malawi said prosecuting President Bashir would polarise all sides in Sudan, driving them away from peaceful settlements in southern Sudan and the western province of Darfur.
Mr Bashir denies the charges against him.