"On February 14, we will all go down to Martyr's Square to say in one voice that the Lebanese are united, that they reject terrorism and that all attempts to intimidate us won't succeed," Hariri said in a fiery speech to a packed audience of party members and supporters.

"On February 14 we will converge on Martyr's Square from all corners of the country to speak out loud in one voice that we want a president... to say that the road to the presidency cuts through Beirut and the parliament building, not through Damascus, Tehran or any other capital," he added.

""We are faced with the political and terrorist presence in Lebanon of the Syrian and Iranian regimes, but we will not sit by and watch.

"If confrontation is our destiny, then we stand ready."

Hariri's father, former prime minister Rafiq Hariri, was killed in a massive car bombing on February 14, 2005, sparking international outrage and leading to the withdrawal of Syrian forces from the country after a 29-year presence.

One month after his death, on March 14, hundreds of thousands of Lebanese flooded into Martyr's Square in central Beirut, near where Hariri is buried, demanding an international enquiry and a withdrawal of Syrian troops.

Syria has denied any involvement in the killing.

A number of anti-Syrian politicians and journalists have also been killed since Hariri's assassination, with the country embroiled in its worst political crisis since the end of the 1975-1990 civil war.

Lebanon has also been without a head of state since November because of the long-running crisis pitting the Western-backed majority headed by Saad Hariri against the Hezbollah-led opposition.

Thirteen attempts since last September to replace former pro-Syrian head of state Emile Lahoud have failed, and lawmakers are scheduled to gather again on Monday to try to elect army chief General Michel Sleiman as president.

Hariri's speech came as Arab League chief Amr Mussa returned to Beirut on Thursday for another attempt at convincing feuding leaders to agree on an Arab initiative that calls for Sleiman's election, a national unity government and the adoption of a new electoral law.

The majority has endorsed the plan but the opposition, backed by Syria and Iran, is demanding a third plus one of the seats in a new government in order to secure veto power.