The United States and European Union have already imposed sanctions on individual commanders from both sides.
South Sudan's warring factions may face further international pressure to end their conflict if they do not reach a peace deal by Aug. 17, US President Barack Obama said on Monday.
Obama, in Ethiopia on a two-nation Africa tour, met regional African leaders on Monday in Addis Ababa to discuss the conflict that flared in December 2013, pitting troops loyal to President Salva Kiir against rebels commanded by Riek Machar.
A US official said sanctions or other penalties could be considered if the two sides failed to reach a peace deal by an August 17 deadline. Previous deadlines have been ignored, deepening the crisis in the world's newest nation.
"If we don't see a breakthrough by the 17th, then we have to consider what other tools we have to apply greater pressure on the parties," Obama told a news conference with Ethiopian Prime Minister Hailemariam Desalegn, who has hosted peace talks.
The United States and European Union have already imposed sanctions on individual commanders from both sides. Obama acknowledged efforts to end the conflict by IGAD, a regional African grouping that has mediated and which includes Ethiopia, but said the "the situation continues to deteriorate."
Hailemariam recognised that negotiations had rumbled along for a long time. "The people are suffering on the ground and we cannot let this go on," he said, adding Monday's meeting with regional leaders should send a "strong signal" to the rivals.
IGAD states threatened sanctions in the past, but did not act on them and more recently said such steps would not help. Western diplomats have pressed the region to put more pressure on the South Sudanese for a deal, saying regional measures were more likely to have an impact on leaders.
The United States, Britain and Norway were among the main Western states that sponsored South Sudan when it seceded in 2011 from Sudan. The southerners had fought Sudan's government for decades, but had also often battled each other. Those at the talks also include Ugandan President Yoweri Museveni, Kenyan President Uhuru Kenyatta, Sudanese Foreign Minister Ibarahim Ghandour and the African Union's Dlamini Zuma.
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