A South Sudanese official has told Al Jazeera that it will release some of the detained politicians accused of links to the alleged coup as early as Saturday in a bid to ease tensions in the conflicted-wracked country.
The continued detention of the politicians had been a major sticking point in the peace talks.
On Friday, leaders of South Sudan's neighbours have said President Salva Kiir committed to an immediate ceasefire as they urged rebel leader Riek Machar to make the same commitment.
A statement issued on Friday after meeting of regional heads of state in the Kenyan capital Nairobi said the east African body Inter-Governmental Authority on Development (IGAD) agreed to consider taking further action if the hostilities did not end within four days of the communique, but did not elaborate on the possible measures.
"[IGAD] welcomes the commitment by the government of Republic of South Sudan to an immediate cessation of hostilities and calls upon Dr Riek Machar and other parties to make similar commitments," a communique from the 23rd Extraordinary Session of IGAD said.
Uhuru Kenyatta, the Kenyan president, urged Kiir and his former deputy Machar earlier on Friday to seize "the small window of opportunity" and start peace talks after nearly two weeks of fighting between government troops and those loyal to Machar.
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"Let it be known that we in IGAD will not accept the unconstitutional overthrow of a duly and democratically elected government in South Sudan. Violence has never provided optimum solutions," Kenyatta said, speaking in Nairobi.
Meanwhile on the ground, government forces and rebels were battling on Friday for control of Malakal, capital of South Sudan's oil-producing Upper Nile State where witnesses reported heavy fighting overnight.
Both government forces and rebels insisted they were in control after days of street battles.
Moses Ruai Lat, a rebel spokesman in Unity State, said "the whole of Malakal" was now in the hands of Machar's loyalists, who already control Bentiu, capital of the neighbouring Unity state.
"All those forces who are loyal to the president have been cleared and the former governor of Upper Nile, Simon Kun Poch, is on the run," Lat told the AFP news agency.
However, Kuol Manyang Juuk, South Sudan's defence minister, dismissed the claim as "disinformation".
"The elements loyal to Riek Machar were defeated and they are no longer in Malakal. The town is under full government control," Juuk said, adding that government troops - the Sudan People's Liberation Army (SPLA) - were reinforcing their presence in the town.
Days of violence
The fighting in South Sudan started on December 15 after Kiir accused Machar, whom he sacked in July, of attempting a coup. Machar denied this, and said the president was exploiting a clash between members of the army as a pretext to carry out a purge.
Fighting has since spread to half of South Sudan's 10 states, with the violence taking on an ethnic dimension - pitting members of Kiir's Dinka tribe against Machar's Nuer community and atrocities reported to have been carried out by both sides.
Witnesses have reported massacres, summary executions and rapes, and UN Secretary-General Ban Ki-moon has promised those responsible would be "held accountable".
The UN says more that 120,000 people have been displaced, including 63,000 sheltering in UN peacekeeping bases. UN special envoy Hilde Johnson has said UN troops are "overstretched" and need extra manpower to be deployed with "unprecedented speed".
The UN Security Council agreed on Tuesday to nearly double the size of its mission known as UNMISS, allowing for up to 12,500 soldiers and 1,300 police, after the violence raged out of control.