The former chief of the main opposition Syrian National Council (SNC) on Saturday urged the United Nations to deploy peacekeepers after UN observers suspended their mission in the country.

"We have to send UN peacekeepers to Syria on a mission with more people who would be able to protect themselves from the violence of the regime," said Burhan Ghalioun, ex-leader and current political bureau chief of the SNC.

"Today, it is clear that one cannot rely on unarmed observers," he said, referring to the decision by UN observers to suspend their mission in Syria, blaming intensifying violence that they said risks civilians lives as well as their own.

Ghalioun's call came after a two-day meeting of the major Syrian opposition factions, which are looking to strike a unity deal and outline a roadmap to follow in the aftermath of President Bashar al-Assad's regime.

The suspension of the UN observer mission was, Ghalioun said, "a clear condemnation by the international community and the (Kofi) Annan mission of the violent and aggressive policy of the Syrian regime."

But he said the peace plan negotiated by Annan, the UN and Arab League envoy for the crisis, could still work if the UN Security Council votes "a resolution under Chapter Seven to force the implementation of the plan by the threat of force."

Chapter Seven of the UN charter, on "action with respect to threats to the peace, breaches of the peace and acts of aggression," grants the UN the power to resort to military force to restore and maintain peace.

Explaining the UN decision, mission head Major General Robert Mood spoke of an escalation in fighting, which limited the observers' capability to observe and report, "basically impeding our ability to carry out our mandate."

The Damascus regime exercised "all necessary pressure to ensure that observers leave the country, allowing Assad arms to kill at will," Ghalioun said.

The call for deployment of UN peacekeepers emerged as one of the strongest messages of the two-day workshop between the opposition factions, which, on another front, have to curb internal disagreements and develop a common vision.

"We discussed forming a preparatory committee that will take all proposals on the common vision and the transition plan and prepare some documents so that they are ready for the meeting in Cairo," Louay Safi, a member of the SNC political bureau told AFP on the sidelines of the meeting.

The SNC-led factions are rushing to come up with a strategy that lays down the founding principles of a democratic future Syria, to be ready for a planned Syria conference in Cairo under the auspices of the Arab League, at a date to be announced later.

But unity has proved elusive for the factions, which are trying to forge cohesion among Syria's array of ethnic and religious groups, including Arabs, Kurds, Sunni Muslims, Alawites, Christians, Druze and others.

Last Sunday, the SNC appointed Kurdish activist Abdel Basset Sayda to replace Ghalioun as its new leader, in a bid to gain broader appeal that could embrace all groups.