Warring factions led by President of South Sudan Salva Kiir and Vice President Riek Machar have declared a new ceasefire after fierce fighting broke out on Saturday.
President of South Sudan Salva Kiir and Vice President Riek Machar, leader of the opposition and a former rebel leader, have ordered their forces to halt fighting and stick to a ceasefire declared after days of bloody clashes which claimed hundreds of lives and displaced thousands.
State Department spokesman John Kirby said Washington welcomed the ceasefire, which was separately declared by the president and vice president late on Monday.
"We strongly urge that the two leaders do everything in their power to ensure these decrees will be fully respected and unfettered humanitarian assistance will be provided to those affected by the violence," Kirby said.
Violence broke out between the rival groups in the city of Juba, the capital, ahead of the fifth independence day of the world's youngest country on July 9.
Some media reports cited the country's Ministry of Health as saying more than 270 people were killed in the latest clashes and thousands have fled the region.
Presidential spokesman Ateny Wek Ateny said the president and vice president spoke over the telephone to end the infighting.
In response to Kiir's declaration of a unilateral ceasefire on Monday, Machar announced he would respect the ceasefire.
"The president has declared a unilateral ceasefire, I want to reciprocate the declaration of unilateral ceasefire," he told the independent Eye Radio.
"All the commanders of [Kiir's] forces are directed to cease any hostility and abide by the order and control their forces," Ateny told Reuters.
Ateny also said, "President Salva Kiir is determined to carry on his partnership with Riek Machar."
Kiir's and Machar's forces struck a peace deal last year ending a two-year-long civil war which began in 2013.
Thousands of people were killed and hundreds of thousands of others were displaced during the conflict.
Under the peace deal former rebel leader Machar was made vice president.
The conflict was based around rivalry between two major ethnic groups: the Dinka led by Kiir and the Nuer led by Machar.
The war started when President Kiir attempted to disarm the Nuer ethnic group.
The fresh wave of violence has led to fears the country may plunge into civil war again.
UN condemns South Sudan violence
UN Secretary-General Ban Ki-moon on Monday condemned the killing of two Chinese peacekeepers in the renewed fighting.
"Let me start by expressing my deep condolences to the families and loved ones of all those who have been killed in the fighting that has consumed Juba over the past four days. I condemn the killing of two Chinese peacekeepers and one UN national staff," the secretary-general told reporters.
"The renewed fighting is outrageous. It is yet another grievous setback. It deepens the country's suffering," he said.
"It makes a mockery of commitments to peace. Many people have been killed in heavy fighting. There are growing fears that many more could die in another round of violence," Ban said.
He urged the leaders of South Sudan to do everything they can to end the dispute.
"My message to President Salva Kiir and first Vice President Riek Machar is clear: do everything in your power to de-escalate the hostilities immediately; order your respective forces to withdraw."