UNITED NATIONS (AP) — Sudanese officials asked world leaders including President Barack Obama on Friday for international support to maintain peace as they near a critical independence referendum on south Sudan that is likely to split Africa's largest country in two.

U.N. Secretary-General Ban Ki-moon, Obama and other leaders addressed concerns that preparations for the Jan. 9 vote are lagging and urged a timely and peaceful ballot to ensure any possible transition is smooth and does not ignite a new civil war.

"There will not be a referendum in time in southern Sudan unless things change and change quickly," Ethiopian Prime Minister Meles Zenawi warned a high-level meeting organized by the U.N. chief.

Obama's presence at the gathering demonstrated deep U.S. interest in Sudan's future. The U.S. has offered Sudan the possibility of restored diplomatic relations if it improves conditions in the conflict-wracked western Darfur region, and does not undermine the referendum.

"What happens in Sudan in the days ahead may decide whether a people who have endured too much war move forward toward peace or slip backward into bloodshed," said Obama. "And what happens in Sudan matters to all of sub-Saharan Africa, and it matters to the world."

Zenawi said issues that still must be addressed include the demarcation of potential borders between north and south. If the problems are not dealt with, "we will have a breakdown of peace."

"Sudan is the most important issue of war and peace in Africa," the Ethiopian leader said. "If we fail, it will be a catastrophe for the whole continent. "

A 2005 peace agreement that ended a 21-year civil war between Sudan's mostly Muslim north and predominantly animist and Christian south set up the a unity government in the capital, Khartoum, as well as an autonomous government in the south. It called for the 2011 referendum on southern independence.

Sudan's Second Vice President Ali Osman Taha pledged "the strongest of commitments" to the agreement, and affirmed again that its "supreme and all important goal ... is sustainable and lasting peace for the people of Sudan, north and south and for our region and beyond ... regardless of the outcome of the referendum."

Taha called for an end to stifling economic sanctions, and for forgiveness of the country's foreign debt.

"We need the full cooperation of the international community ... if lasting peace in my country is to become a viable hope," he said.

Sudanese First Vice President Salva Kiir, a former rebel leader who serves as first vice president in Sudan's unity government while also leading a separate autonomous government in the south, also asked for international support.

"Now, as the greatest moment of our history approaches, it is up to all of us to ensure that the referendum is conducted without delay or reservations," Kiir said. "With your help I'm confident we can achieve our common goals."

A communique issued after Friday's meeting said that next year's referendum would not end obligations by signatories of the five-year-old peace accord to work together for a peaceful transition.

It also expressed worries about ongoing violence in the Darfur region, and "welcomed commitments by the Government of Sudan to end impunity, bring all perpetrators of crimes to justice and protect civilians."

Kenyan President Mwai Kibaki told the U.N. General Assembly's annual ministerial meeting that Sudan's President Omar al-Bashir and Kiir assured him that the referendum will take place as scheduled, and they will accept the vote's outcome.

Kibaki is convening East Africa's Intergovernmental Authority on Development in November to ensure all goes well with the vote. Ban has formed a panel to monitor voting,

"The Sudanese people cannot afford a resumption of conflict," Ban told the gathering. "We must all assist them in finding a peaceful way through one of the most important passages in their country's history."

China also is keenly interested in the future of Sudan. It is a key source of its crude oil, and is the African nation's top supporter on the U.N. Security Council.

"Whatever the result of the referendum, it is crucial to maintain peace in Sudan and the region," said Chinese Vice Foreign Minister Zhai Jun. He also called for increased humanitarian assistance to conflict-wracked Darfur.

Along with the Jan. 9 referendum on southern independence, the oil-rich central region of Abyei is to vote that day whether it should belong in Sudan's north or in a possible new country in the south. Leaders in the Arab-dominated north and mainly black African south are in a tug-of-war over Abyei, home to oil fields worth hundreds of millions of dollars.