The leaders of Sudan and South Sudan held talks over the phone to discuss unrest in South Sudan.
The discussions between Abdel Fattah al-Burhan, leader of Sudan's Sovereign Council, and South Sudanese President Salva Kiir on Sunday evening dwelt on bilateral relations and issues of mutual concern, the council said in a statement.
According to the statement, Burhan was "reassured" about the overall situation in South Sudan.
"The Sudanese government is keen on sustaining security and stability in South Sudan," he stressed.
Kiir, for his part, reiterated his commitment to working to strengthen mutual cooperation between Abuja and Khartoum, the statement said.
"The South Sudanese government is keen on establishing security and stability and normalizing security conditions in the country," he stressed.
The contact came shortly after the US ordered nonemergency government personnel to leave South Sudan amid security concerns.
"Armed conflict is ongoing and includes fighting between various political and ethnic groups. Weapons are readily available to the population," the US Department of State said in a statement.
On Friday, a UN helicopter was targeted in Nasir City of the northeastern Upper Nile State while trying to evacuate soldiers, leaving at least 27 people dead.
The UN said Friday's incident, which could deal a blow to an already fragile peace process, was "utterly abhorrent" and a possible war crime.
A power-sharing agreement between Kiir and first vice-president Riek Machar has been threatened in recent weeks by clashes between their allied forces in the Upper Nile state.
The White Army, a militia Kiir's government linked to Machar's ethnic Nuer community, took control of the Nasir city after clashes with government forces.
South Sudan gained independence from Sudan after a referendum in 2011.
