The United States doubts whether South Sudan's President Salva Kiir and rebel leader Riek Machar have the leadership qualities needed to deliver peace to the country at war since 2013, the White House said on Sunday.
Peace talks last week in the South Sudanese capital Juba need to be more inclusive to succeed, the White House said, adding that it will impose fresh sanctions on anyone who threatens the country's stability.
The statement constitutes tough U.S. language about South Sudan, a country whose independence in 2011 Washington backed after a war with Sudan that lasted decades. Since then, tens of thousands have been killed in a civil war.
"We are deeply concerned about the direction of the current peace process .... A narrow agreement between elites will not solve the problems plaguing South Sudan," said the statement.
It implored the warring parties to implement a ceasefire as a first step and condemned a move by the country's parliament to extend the government's term in office.
"South Sudan's political leaders ... have not demonstrated the leadership required to bring genuine peace ... We remain sceptical that they can oversee a peaceful and timely transition to democracy and good governance," it said.
On June 13, a U.S.-drafted resolution at the United Nations Security Council imposed an arms embargo..
South Sudan's parliament voted this month to extend Kiir's mandate until 2021, a move likely to undermine the peace talks as opposition groups say the change is illegal.
Last week Kiir said he is ready to accept a peace deal to end the war and set up an inclusive new government. The proposed deal would give the country five vice presidents and also covers security and power sharing arrangements.