UN Security Council envoys warned South Sudan’s warring leaders Tuesday they would face sanctions if a civil war that has pushed the young nation to the brink of famine does not stop.

UN Security Council envoys warned South Sudan's warring leaders Tuesday they would face sanctions if a civil war that has pushed the young nation to the brink of famine does not stop.

"The council has made it very clear: that it is prepared to impose consequences if there continue to be spoilers, if there continue to be people carrying out gross violations of human rights," US ambassador to the UN Samantha Power said after meeting with President Salva Kiir.

Representatives of the 15-member council, who were in the capital Juba on a two-day mission, were due also to meet rebel chief Riek Machar.

"We will not tolerate violation of the cessation of hostilities and people who spoil the peace agreement," Power told reporters, in one of the strongest warnings yet.

EU Special Representative to the Horn of Africa, Alex Rondos, also expressed concern "that both sides in South Sudan continue spending their money on arms and fighting for power while South Sudanese citizens are beginning to starve to death".

There is no justification for this humanitarian disaster, he said.

Thousands of people have been killed and more than 1.5 million have fled almost eight months of carnage sparked by a power struggle between Kiir and his sacked deputy Machar, with battles between government troops, mutinous soldiers and ragtag militia forces divided by tribe.

Foreign Minister Barnaba Marial Benjamin told reporters the diplomats would be "shown what South Sudan is doing with regard to peace".