Afghanistan's Taliban have appointed the group's co-founder Mullah Abdul Ghani Baradar as the head of their political office in Doha to lead talks with the United States on ending their 17-year insurgency.
"The esteemed Mullah Abdul Ghani Baradar has been appointed … chief of the political office," Taliban spokesman Zabihullah Mujahid said in a statement released late on Thursday.
"This step has been taken to strengthen and properly handle the ongoing negotiations process with the United States," he said.
The announcement came after the Taliban revealed that they had held four straight days of talks with US officials in Doha. Washington confirmed on Tuesday that talks were being held in Qatar between its envoy for Afghanistan Zalmay Khalilzad and representatives of the Taliban, but not made any further comment.
It was not clear if the negotiations continued on Friday.
Mr Khalilzad has held several rounds of talks with Taliban representatives since being appointed last year, including in Abu Dhabi last month, but the length of latest talks has raised hopes of progress towards organising peace talks.
The Taliban have so far refused to hold talks with the Afghan government, which they describe as a US puppet, and have continued to carry out attacks on Afghan security forces, including an assault on an intelligence services base this week in which dozens of soldiers were killed.
Mullah Baradar, formerly deputy chief of the Taliban, helped Mullah Omar to found the Islamist movement that ruled Afghanistan from 1996 until the US-led invasion in 2001.
He was arrested in Pakistan in 2010 and released in October after Mr Khalilzad reportedly held his first meeting with the Taliban in Doha. Mullah Omar died in 2013.
Kabul-based military analyst Ateequllah Amarkhail said Mullah Baradar was a "heavyweight" who also has influence over Mullah Muhammad Rasool, the leader of a Taliban breakaway faction.
"The appointment of Baradar could unify the Taliban movement," Mr Amarkhail told Agence France-Presse.
The Taliban said that in addition to the appointment of Mullah Baradar, "multiple changes have also taken place in the military and civilian departments".
Neither side has released details of the negotiations so far but the Taliban have repeatedly called for the withdrawal of the US-led Nato force in Afghanistan.