The United States on Sunday sent its congratulations to South Sudan as the African nation was set to mark its first year of independence, but said "significant challenges" lay ahead for Juba, AFP reports.
"On behalf of President (Barack) Obama and the people of the United States, I am delighted to send best wishes to the people of the Republic of South Sudan as you celebrate your first anniversary of independence this July 9," Secretary of State Hillary Clinton, who was traveling in Asia, said in a statement.
Clinton noted that South Sudan had made strides in nation-building and on building a legal framework.
"Your work to provide security, accountability and systemic respect for human rights is admirable," she said.
Yet "despite the progress, significant challenges remain that threaten stability and prosperity," Clinton warned.
"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."
South Sudan's independence came at a cost of millions of lives lost during nearly 50 years of civil war against Khartoum, and the year-old country remains one of the world's least developed nations.
The halting of crude production in landlocked South Sudan in January triggered heavy fighting along the disputed border with Sudan.