Hours later, Hezbollah chief Hassan Nasrallah, in a televised address, urged thousands of protesters in central Beirut not to resort to violence and vowed never to turn the group's weapons on civilians.

"Negotiate with us and we will talk to you," Nasrallah said, addressing what he called the "illegitimate Government" of Fouad Siniora.

"But in the name of all those gathered here, we will not leave the streets before achieving the goal that saves Lebanon."

The heavily criticised Lebanese President, an avowed ally of Nasrallah, is at the centre of a looming constitutional crisis overboth the international tribunal and Hezbollah's plans to oust the elected pro-Western Government.

Mr Lahoud said Lebanon would prosper if it aligned with Syria, a regime that has been blamed for causing much of Lebanon's instability through attempts to reassert its influence after having been forced to flee 20 months ago.

As Hezbollah-backed demonstrators continued to lay siege to the main government building in Beirut and the nearby Martyr's Square, Mr Lahoud said: "I can assure you that there will not bea civil war, there will not be aconflict. We will not let thathappen, whatever it takes. Unity is the only salvation for Lebanon." However, he strongly backed the toppling of the Government of Mr Siniora and the rise of a new regime that would effectively give Hezbollah a veto on major decisions through the support of its largely Christian support base in a new parliament.

He said Hezbollah had no interest in turning its weapons on Lebanese civilians and claimed no other sectarian group was well enough armed to launch a violent revolution, because of a weapons amnesty that followed the 15-year civil war. "They don't have the armaments they used to have during the war," he said.

Mr Lahoud, a Maronite Christian, praised Hezbollah, whom he insisted had defeated Israel during the recent 34-day war.

"Believe me, they were defeated. And if it wasn't for the resistance, Israel would be back in Beirut, like it was in 82," he said.

His presidency has been under Western boycott because of his pro-Syrian stance and because the former head of his security detail was one of four generals arrested after the assassination 21 months ago of former prime minister Rafik Hariri.

A UN terrorism probe last year made findings against a spate of pro-Syrian figures and has backed a full international tribunal as a means to defuse rampant conspiracy theories.

But Mr Lahoud said he was sceptical about the UN's motives, claiming they had been influenced by French President Jacques Chirac. "We thought the UN was an independent broker," he said. "But we have opened our eyes and seen that maybe they are operating their investigation for political purposes."

The tribunal is heavily opposed by Syria -- and Hezbollah, which has been widely accused of doing the bidding of Damascus.

The mooted overthrow of Mr Siniora's administration and formation of a "national unity government" is seen as a manoeuvre to derail the tribunal's implementation.