"The US Department of State warns US citizens against all travel to the Republic of South Sudan and recommends that US citizens currently in South Sudan depart immediately," read the statement.
"As a result of the deteriorating security situation, the Department of State ordered the departure of most remaining US government personnel from South Sudan Jan 3, 2014," the statement added.
Clashes in South Sudan have left some 1,000 people dead
It said that the US embassy in Juba "is therefore no longer able to provide any consular services" to US citizens in South Sudan, adding that "citizens who are in need of emergency assistance in South Sudan should contact the US embassy in Nairobi."
During the past two weeks, South Sudan has been witnessing violent clashes between government troops and forces loyal to former vice-president Riek Machar, who is accused of plotting to topple the government.
The clashes have left some 1,000 people dead, over 121,600 civilians displaced and some 63,000 others taking refuge at various UN compounds around the country, according to UN reports.