Dancing and singing, South Sudanese on Monday put aside dire warnings over the stability and economic viability of their fledgling nation, the world's newest, to celebrate its first year of independence.
Celebrations began at midnight as crowds took to the streets of the capital Juba, with people crammed into cars driving around the city and honking horns to mark the first anniversary since separating from former civil war foes in Sudan.
"It is a good day because it's the first birthday of my country," said Rachel Adau, a nurse, who arrived soon after dawn to secure a place at the official ceremony, held at the mausoleum of the late rebel leader John Garang.
"Today is the day we celebrate when the people came out from the Arabs and liberated themselves," said Michael Kenyi Benjamin, a student.
South Sudan has spent the past year wracked by border wars with the rump state of Sudan, as well as internal violence and the shutdown of its vital oil production in a bitter dispute with Khartoum.
Vice President Riek Machar has admitted to failing to meet his people's expectations because of "the unforeseen difficulties we got ourselves into."
The early euphoria of independence on July 9, 2011, has since given way to a harsh reality.
While massive steps forward have been made, South Sudan remains one of the world's poorest countries, where even the most basic infrastructure, such as roads, electricity and water distribution networks, is lacking.
United Nations chief Ban Ki-moon and African Union commission chairman Jean Ping are expected to attend a military parade and official speeches, scheduled to begin around midday (0900 GMT).
No senior Sudanese officials are expected to attend, according to an official programme, in a sharp contrast to last year, when Sudanese President Omar al-Bashir was greeted warmly as he witnessed the end of a unified Sudan.
Tension remains high with Khartoum after heavy border fighting in March and April along oil-rich disputed frontier regions.
Other guests include former South African president Thabo Mbeki, who is mediating AU-led talks between Sudan and South Sudan, as well as the leaders of Ethiopia, Kenya and Uganda.
The United States on Sunday sent its anniversary congratulations, while admitting that "significant challenges" lie ahead.
"Conflict and unresolved issues with Sudan and domestic inter-ethnic tensions have led to increased fighting and economic hardship, which threatens to compromise the very foundation on which South Sudan's future will be built," Secretary of State Hillary Clinton said in a statement.
Nobel Peace Prize laureate Desmond Tutu appealed for peace in the troubled fledgling nation.
"God wants to make South Sudan prosperous and peaceful," the 80-year-old retired South African archbishop told political, military and religious leaders in Juba ahead of Monday's celebrations.
"We want to return to come again and celebrate your nationhood with you and see a South Sudan that grows its own food and is eradicating poverty and ignorance," Tutu said.