After decades of brutal war which killed two million people, oil rich South Sudan finally becomes independent from Sudan's Khartoum ruled north on Saturday, in an emotional celebration to be witnessed by a host of foreign dignitaries, including Vice President Hamid Ansari.
Some 99% of southern Sudanese had voted for independence from the north of Sudan in a referendum held in January. The poll was agreed as part of the 2005 deal to end the civil war.
However, recent clashes between Sudanese military and Southern Sudanese forces in the Southern Kordofan region have raised concerns that conflict could flare up again.
"This is a fragile and fraught moment as well. It cannot and must not be taken for granted," US ambassador to the UN Susan Rice, who is leading a bipartisan American delegation to the independence celebration in Juba, the capital of South Sudan, said on Thursday.
She asked the northern and southern governments to resolve issues related to the resource rich area of Abyei and other border regions.
South Sudan had reached a comprehensive peace agreement with North Sudan in 2005, brokered by US secretary of state Colin Powell under former President George W Bush, that stopped the civil war and paved the way for the January referendum.