Taban Deng’s comments came as the two sides hold ceasefire talks in Ethiopia’s capital, Addis Ababa.
Information Minister, Michel Makuel said that the Government is committed to ending the conflict.
The conflict pits supporters of Mr Kiir against rebels led by his sacked deputy, Riek Machar.
At least 1,000 people have been killed since violence erupted on December 15.
The violence started after Mr Kiir accused Mr Machar of attempting a coup, that is still an allegation which he denies.