Al-Assad's visit would be his first since the 2005 assassination of Rafiq al-Hariri, Saad's father and the former prime minister of Lebanon.

The killing, blamed by many on Syria, soured relations between the two countries. But ties have been on the mend since 2008 when diplomatic relations were established for the first time between Lebanon and Syria.

'Arab unity tour'

News of al-Assad's visit comes as King Abdullah continues his four-nation "Arab unity tour".

Following his visit to Egypt for talks with Hosni Mubarak, the president, on the Arab-Israeli peace process, the Saudi king arrived in Syria on Thursday. The tour would also take him to Jordan, besides Lebanon.

The Lebanon trip is aimed, in part, at reducing tensions over the Special Tribunal for Lebanon, the UN-backed body investigating the murder of al-Hariri.

Hassan Nasrallah, the leader of Hezbollah, last week alleged that the special tribunal was set to indict his group for al-Hariri's murder, triggering fears of a Shia-Sunni conflict being reignited in Lebanon.

There is also concern a new conflict might be looming between Hezbollah and Israel, which in recent months has accused the Lebanese group of stockpiling weapons in preparation for a new war.

The two foes fought a devastating war in 2006 that left much of Lebanon's infrastructure in ruins.

Shadi Hamid, the deputy director of the Brookings Doha Center, said: "I think the next two weeks will be crucial.

"There is a risk of escalation, of sectarian violence, and all players involved realise that risk and are taking pre-emptive action to defuse things before they get out of hand in the next weeks and  months," Hamid told the AFP news agency.