US seeks UN vote on South Sudan arms embargo

US Ambassador Samantha Power made the case for cutting off the weapons flow to the war-torn country during a council meeting, arguing that all sides were mobilising for more fighting and that action was needed to prevent mass atrocities.

"The situation is not getting better, but worse, and we are sitting on our hands," Power told the council. "Large-scale attacks could start at any moment."

The United States last month presented a draft resolution on imposing an arms embargo following UN warnings that the war-torn country could descend into genocide.

An annex to the proposed resolution would also put South Sudan's rebel leader Riek Machar, army chief Paul Malong and Information Minister Michael Makuei on a sanctions blacklist.

The United States will request a vote on the arms embargo before the end of the year, Power said.

UN Secretary General Ban Ki-moon backed the US call to ban arms deals with South Sudan, saying an embargo would reduce the capacity of all sides to wage war.

"If we fail to act, South Sudan will be on a trajectory towards mass atrocities," said Ban.

Russia sees no risk of genocide

France and Britain support an arms embargo, which could come up for a vote as early as Thursday, according to diplomats.

But veto powers Russia and China have voiced opposition, while non-permanent council member Japan, which has sent peacekeepers to South Sudan, is also balking at the proposal.

Japan has argued that imposing an arms embargo would antagonise President Salva Kiir's government and put peacekeepers' lives at risk in a conflict already marked by horrific levels of brutality.

Russian Deputy Ambassador Petr Iliichev cast doubt over UN warnings of a risk of genocide, arguing that criminal groups and "undisciplined" troops were responsible for mass violence, and not the government's policy.

"We would refrain from concluding that there is any form of targeted systemic policy," he told the council.

UN aid chief Stephen O'Brien said the humanitarian crisis had "deteriorated dramatically" as South Sudan entered its fourth year of war.

More than 6 million people - half of South Sudan's population - are in need of urgent aid and humanitarian organisations expect this number to rise by 20 to 30 percent next year, O'Brien told the council. 

Some 1.3 million South Sudanese have fled across borders as refugees, including 383,000 who have fled to Uganda since July, according to UN figures. 

The world's youngest nation, South Sudan descended into war in December 2013, leaving tens of thousands dead and more than 3.1 million people displaced.

The country won independence from Sudan in 2011 with strong support from the United States.