Violence is spreading across Khartoum as riots began after ex-rebel leader John Garang died.
Tear gas has been used and a military helicopter is flying low over the city centre, where gangs of men with clubs and automatic weapons are roaming.
There are traffic jams as residents try to flee. In three days of violence the death toll has risen to 84.
US envoys are to meet Mr Kiir, who told the BBC “nobody wants war” and reiterated his commitment to the peace process.