China on Friday voiced opposition to a UN draft resolution on imposing sanctions on South Sudan, saying the measure would be unhelpful at a time when the warring factions are negotiating.

The United States presented a draft text to the Security Council this week that provides for sanctions against individuals seen as blocking efforts to end the 14-month war in South Sudan.

But Chinese Ambassador Liu Jieyi told reporters that negotiations on a final peace deal had entered a difficult phase and suggested that sanctions would complicate the talks.

"Sanctions are a punitive thing to do. I think there is no misunderstanding about that," Liu said.

"They are walking to the negotiation table, they are talking across the negotiating table. To apply a punitive measure now would send out what kind of message? Right message or wrong message?"

A new round of negotiations between the warring sides opened in Ethiopia on Monday, brokered by the eight-nation IGAD (Intergovernmental Authority on Development) regional group.

The talks are focused on reaching a final peace deal between President Salvaa Kir and rebel leader Riek Machar that includes a transitional unity government, even though the previous agreements have failed to take hold.

The Chinese envoy said the sides had settled "90 percent" of their differences and that the remaining issues dealing with power-sharing were understandably "more difficult."

"At this moment, when the two sides are negotiating for a solution, you talk about imposing sanctions. Frankly I don't see the logic behind this, and we have never seen sanctions as something that should be applied simply for the sake of applying sanctions," he said.

Tens of thousands of people have died in the violence that began in December 2013 after a falling-out between Kiir and Marchar, then his vice president.

More than 1.5 million civilians have fled fighting and 2.5 million are in dire need of food aid in South Sudan, which declared independence from Sudan in 2011.

China has invested heavily in South Sudan's oil production, which has been badly affected by the fighting.