* Envoys' trip meant to hasten ceasefire deal
* South Sudan govt. delegation optimistic on deal
By Aaron Maasho
ADDIS ABABA, Jan 11 (Reuters) - Three African envoys headed to South Sudan on Saturday to try to persuade rebel leader Riek Machar to accept a ceasefire deal to end fighting that has driven the world's youngest nation to the brink of full-blown civil war.
More than three weeks of fighting between President Salva Kiir's SPLA government forces and rebels loyal to former vice president Machar have killed more than 1,000 people, driven 230,000 from their homes and forced a cut in oil production.
Kiir's information minister said he believed the ceasefire deal, which the two sides have been haggling over in face-to-face talks in neighbouring Ethiopia since Tuesday, could be signed once the envoys return to Addis Ababa.
"The negotiators travelled to South Sudan this morning to meet Riek Machar. The aim is to expedite the signing of a cessation of hostilities agreement," a diplomat close to the talks told Reuters.
Machar's whereabouts have not been disclosed by members of his delegation at the Addis Ababa talks. But sources at the talks say he is in a town in South Sudan's strife-torn Jonglei region close to the border with Ethiopia.
A draft copy of the ceasefire deal drafted by mediators envisages monitoring mechanisms to ensure full implementation. The ceasefire has been held up by rebel demands for the release of 11 politicians allied to Machar and detained since December.
"We are optimistic that we will sign the cessation of hostilities agreement as soon as the envoys are back from their mission, said South Sudanese Information Minister Michael Makuei, who heads the government's delegation in Addis Ababa.
South Sudan's army said on Friday it had regained the rebel-held town of Bentiu, restoring government control of Unity state where oil production had been halted by fighting.
The rebels said they made a "tactical withdrawal" from Bentiu to avoid civilian casualties.
South Sudan's oil production fell by 45,000 barrels per day to 200,000 bpd after oilfields in Unity state were shut down due to fighting. Upper Nile state is still pumping about 200,000 bpd, according to the government.
The conflict in South Sudan has caused unease among the country's main Western backers and neighbours.
Sources briefed on U.S. discussions told Reuters Washington was weighing targeted sanctions against South Sudan due to its leaders' failure to end the crisis. Such sanctions focus on individuals, entities or sectors in a country.
The possibility of sanctions against a country Washington helped create in 2011 shows how frustrated President Barack Obama's administration has become with Kiir and the rebels.
Largely Christian South Sudan gained independence from predominantly Muslim Sudan in 2011 after a referendum was held in keeping with a 2005 U.S.-backed peace deal that ended a north-south civil war that had left millions dead. (Editing by James Macharia and Gareth Jones)
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