Syrian Vice-President Abdul Halim Khaddam has resigned from the government and the ruling Baath party.
Mr Khaddam is said to have made his announcement during a meeting of the Baath party on the first day of a conference focusing on reform.
No reason has been given for his resignation and it is not known if the party has accepted it.
Mr Khaddam, a veteran hardliner, is seen as an architect of Syrian influence in neighbouring Lebanon.
BBC regional analyst Daniel Nassif says Mr Khaddam’s influence has grown weaker recently.
International pressure earlier this year forced Syria to withdraw the troops it had sent to Lebanon during the 1975-1990 civil war.
Reform conference
Mr Khaddam was born in 1932 and is one of Syria’s oldest leaders, having worked for Hafez al-Assad, father of the current leader, Bashar al-Assad.
He was a foreign minister and deputy prime minister in the Baath party before he was promoted to vice-president in the 1980s.
For decades, he charted Damascus’ policy towards Beirut. He was quoted in 1976 as saying: “Lebanon will either be united or will be returned to Syria.”
No explanation has been offered for his resignation, which comes at the start of a Baath party conference that is expected to recommend opening up Syria’s economic and political life.
A party source told the Reuters news agency that Mr Khaddam expressed his wish to step down “during a meeting of the political committee of the party to which resignations are not normally submitted”.
“It can neither accept nor reject any resignation,” the source was quoted as saying.
