JUBA, South Sudan (AP) _ South Sudan became the world's newest nation early Saturday, officially breaking away from Sudan after two civil wars over five decades that cost the lives of millions.

   In the new country's capital, Juba, streets pulsed with excitement. Residents danced, banged on jerry cans and chanted the name of the world's newest president, Salva Kiir. One man kneeled and kissed the ground as a group ran through the streets singing ``We will never, never, never surrender.''

   ``Ah, I'm free,'' said Daniel Deng, a 27-year-old police officer and former soldier who broke out in a wide grin.

   The Republic of South Sudan earned independence at 12:01 a.m. Saturday, breaking Africa's largest country in two. It marked the culmination of a January independence vote, which was guaranteed in a 2005 peace deal that ended the most recent north-south war.

   After the celebrations die down, residents of South Sudan face an uphill climb. While the new country is oil-rich, it is one of the poorest and least-developed places on Earth. Unresolved problems between the south and its former foe to the north could mean new conflict along the new international border, advocates and diplomats warn.

   Saturday's early morning celebrations were joyous for the freedom gained but tinged with the memories of family lost. At least 2 million people were killed in Sudan's last civil war, fought from 1983-2005.

   ``I came here for this moment,'' said Chol Allen, a 32-year-old minister who escaped Sudan in 2003 and eventually settled in Memphis, Tennessee. He returned to Juba two months ago for the midnight party, though he plans to go back to the U.S., where he has a 4-year-old daughter.

   ``We were all born into war. All of us,'' he said, then pointed at a crowded pick-up truck of youngsters. ``This generation will see the hope of the newborn nation.''

   John Kuach, a former child soldier who joined the army after his father died in fighting with the north, first fought at age 15. At dinner late Friday, he draped the South Sudan flag around his shoulders and called Saturday ``a big day.''

   ``But some people are not happy because we lost heroes, those who were supposed to be in this celebration. So we are thinking, 'Is this true? Is this a dream? A new country?'''

   The internationally brokered 2005 peace deal that ended more than two decades of north-south war expires at midnight Friday. That's when Sudan _ which South Sudan is breaking away from _ officially recognized the new country.

   South Sudan is expected to become the 193rd country recognized by the United Nations next week and the 54th U.N. member state in Africa.

   Later Saturday, world leaders will attend a celebratory ceremony. U.N. Secretary-General Ban Ki-moon already has arrived. Former U.S. Secretary of State Colin Powell also will attend, as will Sudanese President Omar al-Bashir, whose country already has recognized South Sudan.

   The young government faces the huge challenge of reforming its bloated and often predatory army, diversifying its oil-based economy, and deciding how political power will be distributed among the dozens of ethnic and military factions. It must also begin delivering basic needs such as education, health services, water and electricity to its more than 8 million citizens.

   Abdule Taban wore a wide smile during the night's street party, but the 25-year-old was also reflective.

   ``In independence we are going to have hospitals and schools and a lot of development around here. Our mothers and sisters died in the past. Hospitals were very far from us,'' said Taban, as South Sudanese dusted in white cow dung _ a traditional camouflage here _ danced around him.

   A draft constitution passed this week lays the groundwork for the president and legislators, who were elected last year, to serve out their five-year terms. The legislature's few opposition lawmakers are unhappy with the draft, but it now serves as an interim constitution until multiparty elections are held.

   A $1 billion yearly U.N. peacekeeping mission with a 10,000-member peacekeeping force has monitored implementation of the 2005 peace deal. The mission has drawn criticism for its failure to protect Sudanese civilians caught in violence along the north-south border and in the south, where conflict has killed nearly 2,400 people this year alone.

   The U.N. Security Council on Friday unanimously approved a new peacekeeping force for South Sudan, authorizing the deployment of up to 7,000 military personnel and 900 international police, plus an unspecified number of U.N. civilian staff including human rights experts.

   The Obama administration has devoted considerable time to ensuring the fragile peace deal holds.

   With the raising of South Sudan's flag in the world's newest capital, Juba, the international community may breathe a collective sigh of relief that independence has been reached. Al-Bashir has pledged to accept losing about one-third of his country's territory, an area that contains valuable oil fields.

   But relations between the two already are looking bleak, with hostilities raging between northern troops and southern-allied forces in a northern border state, a tense stalemate over another disputed border zone, and a breakdown in negotiations this week over the future of Sudan's oil industry.

   While South Sudan is now expected to control of more than 75 percent of what was Sudan's daily oil production, it has no refineries and southern oil must flow through the north's pipelines to reach market.

   North-south negotiations under way in the Ethiopian capital this week broke down over disputes between the two sides over how to resolve the ongoing crisis in the Nuba Mountains region in northern Sudan, where black Africans from the Nuba tribe have taken to caves to take shelter from aerial bombing by the northern army in the past month.

   Western diplomats say hostilities in that area have stymied efforts to resolve other critical outstanding issues between the governments. Princeton Lyman, the U.S. envoy to Sudan, said Friday that relations between the south and north will be ``strained and a little rocky.''

   ``I don't expect that these countries are going to love each other but I do think they are bound up in each other,'' he said, citing the dependence north and south have on each other for trade and especially oil, which is the lifeblood of the economies of both governments.

   Oil has been a major sticking point at the negotiating table, and tensions worsened after the northern army's seizure of the disputed zone of Abyei in May.

   Despite calls from the Security Council and others to remove its troops from Abyei after they displaced about 100,000 residents, the Sudanese Armed Forces continue to occupy the Texas-sized territory.

   The 1,300-mile (2,100-kilometer) border is disputed in five areas, several of which are being illegally occupied by either northern or southern troops.

   ``Everyone is for peace in and between Sudan and South Sudan,'' said John Prendergast, founder of the Washington-based Enough Project.

   ``It is clear that as long as the government of Sudan can without consequence militarily occupy Abyei, bomb the Nuba Mountains, continue military operations in Darfur, and support militias in southern Sudan, then there will be no peace,'' said Prendergast, who urged the U.S. government to work with allies to create ``significant costs for ongoing human rights abuses and broken agreements.''