UNITED NATIONS (AP) -- The U.N. Security Council warned Thursday of "costs or consequences" for South Sudan's government and opposition if they undermine upcoming efforts to achieve a cease-fire and implement a 2015 peace agreement.
The council underlined in a presidential statement approved by all 15 members that "no party should set preconditions to participation" in the new peace process.
Council members strongly backed the forum organized by an eight-nation East African regional group to revitalize peace efforts. It is expected to begin Monday in Ethiopia's capital, Addis Ababa.
There were high hopes that South Sudan would have peace and stability after its independence from neighboring Sudan in 2011. But the world's newest nation plunged into ethnic violence in December 2013 when forces loyal to President Salva Kiir, a Dinka, started battling those loyal to his former vice president, Riek Machar, a Nuer.
An August 2015 peace agreement has not stopped the fighting, and clashes in July 2016 between supporters of Kiir and Machar set off further violence. The conflict has killed tens of thousands of people.
The Security Council expressed deep concern that all parties are perpetuating the conflict, which it said has led to 7.6 million people in need of aid, 4 million displaced, and 6 million lacking enough food to feed themselves.
U.N. humanitarian chief Mark Lowcock warned last week that over 1.2 million people in South Sudan are one step away from famine - twice as many as at the same time last year. He said that by early 2018, half the country's population will be relying on emergency food aid.
As a first priority, the Security Council called on all parties to end hostilities "as a sign of commitment" to the peace forum organized by the East Africa regional group, "as they have pledged to do."
The council urged the rival parties "to agree to monitored, effective, and durable security arrangements to stop the conflict," to improve human rights and humanitarian access, and to implement government arrangements that represent "all voices in South Sudan."
Council members also called for the parties to agree to a political process leading to "viable elections," timelines to implement the agreements reached, and "strong monitoring and enforcement mechanisms" to ensure that all agreements are carried out.
"There must be cost and consequences for those who undermine" the peace process, the statement said.
Britain's U.N. ambassador, Matthew Rycroft, told reporters that if the parties fail to engage in the revitalization effort, "then the sort of consequences we're talking about are either imposing an arms embargo and/or introducing targeted sanctions."
The council voted unanimously to extend the mandate of the U.N. peacekeeping force in South Sudan until March 15, 2018. Rycroft said the council decided to extend the mission for only three months rather than a year "to keep the feet of the parties to the fire, make sure that they really uphold their obligations and our expectations."