The US has recalled its ambassador to South Sudan following the failure of President Salva Kiir and his rival Riek Machar to form a joint government as agreed in a peace deal.
The State Department said Thomas Hushek would return to help the US re-evaluate its relations with South Sudan following the leaders’ failure to form a unity government by 12 November.
On 7 November President Kiir and his former deputy Mr Machar agreed to postpone the formation of the joint government for 100 days.
Civil war broke out in 2013 when the two men fell out.Thousands of people have been killed and at least four million people have been displaced.
A power-sharing agreement was signed between the warring parties in August 2018 in a bid to bring the five-year civil war to an end.
The US is however frustrated by the failure of the two main protagonists to adhere to plans for a transitional government.
US sends South Sudan about $1bn (£775m) in aid annually.