The US has said it is "deeply concerned" by reports of violations by both the South Sudanese government and the rebel forces of a ceasefire agreement signed in January.
"We urge the redeployment or phased withdrawal of foreign forces invited by either side, and warn of the serious consequences which could result from any regionalisation of this conflict," Xinhua quoted Jen Psaki, spokeswoman of the US State Department, as saying in a statement.
The US also strongly urges the South Sudanese government to facilitate the work of a team that has arrived in Juba, the country's capital, to monitor and verify the implementation of the ceasefire agreement, Psaki said.
The ceasefire agreement, which was inked Jan 23, seeks to ease a political dispute in the world's youngest nation between President Salva Kiir and his former deputy Riek Machar, who was removed from office in July 2013 and later accused of attempting a coup.