"We are leading the Arab League to reaching the position that they have failed in protecting people in Syria," he said. "But we still want the Arab League to make the calls and take the initiative, so we are pushing them to call for a UN Security Council resolution."
Arab League ministers are due to meet in Cairo on Saturday to decide whether or not to allow the observer mission to continue. Hamad bin Jassem al-Thani, the Qatari minister who leads the League's Syria steering committee, acknowledged yesterday that the observer mission had made "mistakes" but there were growing signs that the monitors would be given a reprieve.
Although the League has threatened to refer Syria to the Security Council if Mr Assad is shown not to have ended the violence against his own people, it is far from clear whether it has the collective will to do so.
And while a resolution with Arab backing would make it harder for Russia and China to continue backing Syria at the UN, there are also doubts whether Western powers have the appetite to do anything more than impose sanctions against Damascus.
Mr Ghalioun insisted that the opposition only needed limited military assistance, calling for the creation of a "safe zone" in and around the restive of Idlib, close to the Turkish border where the rebel Free Syrian Army has its headquarters.
Although such a haven would require protection from the skies, a mission on the scale of Libya need not be undertaken, he claimed.
"We don't have to destroy all the Syrian airforce," he said. "You only need to secure a specific zone and this can be done without damaging the whole defences of the country.
"We believe that a safe zone will encourage battalions and armies of the regime to defect and take the side of the revolution. This would topple the balance of power in the favour of the revolution."
A limited operation on the scale proposed by Mr Ghalioun is likely to rule out American involvement because US rules of engagement dictate that a no-fly zone can only be mounted over a territory where potentially hostile air defences have first been neutralised. Mr Ghalioun's call for a no-fly zone represents a major policy reversal. In an attempt to unite with domestic dissident groups, the Syrian National Council, which is dominated by exiles like Mr Ghalioun, agreed last week to drop calls for non-Arab military intervention.
But he changed his mind after protesters on the streets of Syrian cities denounced the compromise.
Western powers have grown frustrated by divisions within the Syrian opposition. Belgium's foreign minister, Didier Reynders, held talks with rival opposition groups yesterday to seek to mend a rift that, he warned, was "playing into the hands of the Syrian regime."
Despite the frustration, Mr Ghalioun has won widespread praise in Western capitals after pledging that a post-Assad government would end military ties with Iran and end Syria's policy of providing arms and financing to Hamas and Hizbollah, the anti-Israel Islamist groups.