Syria has invited the prime minister of Lebanon to an Arab summit in March, in the absence of a Lebanese president.
The invitation was not given directly to Mr Siniora
Lebanon has been in crisis and without a president for months, with pro- and anti-Syrian factions deadlocked.
There had been speculation over which side would be invited. Prime Minster Fouad Siniora is a leading anti-Syrian.
Egypt and Saudi Arabia are said to be threatening to boycott the talks, blaming stalled attempts to elect a new president on Syrian interference.
It is not clear if Mr Siniora will accept Syria's invitation to the 29 March summit.
He was in Senegal at the time the invitation was issued, and it was not delivered directly to his office.
It was instead given by Syria's Assistant Foreign Minister Ahmad Arnous, the first Syrian official to visit Lebanon for 18 months, to the pro-Syrian, outgoing Lebanese Foreign Minister Fawzi Salloukh.
"Due to the presidential void, Lebanon will choose the person who will represent it at the summit and Syria will receive them cordially," a Syrian foreign office quoted Mr Arnous as saying.
Mr Saloukh is one of six pro-Syrian Cabinet ministers who resigned in November 2006 in one of the many twists in the drawn-out power struggle between the pro- and anti-Syrian factions.
The political process had been paralysed since pro-Syrian President Emile Lahoud stepped down at the end of his presidency in November 2006.
It is not clear whether Mr Siniora will attend the summit
Although the two sides eventually agreed late last year on a compromise candidate, army commander General Michel Suleiman, all attempts to elect him have failed.
The pro-Syrian faction - led by the Shia Muslim group Hezbollah and a Christian party - has refused to back his election unless their demands for increased powers in government are also met.
Mr Siniora heads the US-backed, anti-Syrian bloc, which brings together Christian, Sunni Muslim and Druze parties.
Sixteen parliamentary sessions have failed to break the deadlock. A new session is scheduled for 25 March, just days before the Damascus summit.
Syria ended its 29-year presence in Lebanon in 2005, after popular protests in the wake of the death of former Lebanese Prime Minister Rafik Hariri in a car bombing.
Damascus has been implicated in the death by the UN, but denies involvement.