This follows the US’s criticism of Russia for resisting tougher UN action.
Syrian rebels threatened to escalate their operations unless the government of President Bashar al-Assad falls in line by midday (0900 GMT) on Friday with a six-point peace plan brokered by UN-Arab League peace envoy Kofi Annan.
Ban, addressing a forum in Istanbul, made it clear he too expected Damascus to implement Annan’s blueprint, which includes a ceasefire that should have taken effect on April 12 but has been violated daily ever since.
”I demand that the government of Syria act on its commitment to the Annan peace plan,” the UN chief said.
”The massacres of the sort seen last weekend could plunge Syria into a catastrophic civil war, a civil war from which the country would never recover.”
He was referring to a slaughter near the central town of Houla on Friday and Saturday of 108 people, including 49 children and 34 women.
The assault prompted Western governments, including the United States, Britain, France and Australia, to expel the senior Syrian diplomats in their countries.
In Denmark, US Secretary of State Hillary Clinton warned that Russia’s policy of resisting UN Security Council action against Damascus could contribute to a civil war.
The Russians ”are telling me they don’t want to see a civil war. I have been telling them their policy is going help to contribute to a civil war,” she told a mainly student audience in Copenhagen.
Clinton warned that unless checked, the deadly violence in Syria could even develop into a proxy war because of Iran’s support for the Assad’s regime.
A team led by Annan visited Syria earlier this week and called for ”concrete gestures” from Assad on halting the violence.
But with Annan receiving no firm commitments from the Syrian leader, the rebel Free Syrian Army’s command inside the country gave the president an ultimatum on Thursday.
A statement said that if the regime ”does not meet the deadline by Friday midday, the command … will no longer be tied by any commitment to the Annan plan … and our duty will be … to defend civilians.”
Speaking in reaction to the ”barbarous” massacre, the FSA said ”there is no more justification for us to unilaterally respect the truce because (Assad) has buried Annan’s plan.”
It said it would announce in the coming days ”a series of decisive and courageous decisions for the next phase” of its struggle.
Indicating serious divisions within the ranks, Turkey-based FSA chief Colonel Riyadh al-Asaad prompted a sharp retort from the leadership inside Syria after he denied there had been an ultimatum.
Colonel Kassem Saadeddine, speaking to AFP from Syria, said: ”From now on, all decisions will be taken from inside Syria. Anyone who wants to speak in the name of the FSA should do it from the battlefield, not through media.”
The United States, France, Britain and Germany all emerged from a Security Council meeting on Wednesday urging stronger measures by the body.
US ambassador Susan Rice said if Damascus did not adhere to the Annan plan, then the council had to ”assume its responsibilities” and step up pressure.
In the absence of either scenario, and if the violence continued to worsen, ”then members of this council and members of the international community are left with the option only of having to consider whether they’re prepared to take actions outside of the Annan plan and the authority of this council.”
Her remarks appeared to signal that Washington and its allies would consider acting alone if Russia and China continued to block tough action.
But the US envoy to NATO said on Thursday military action was not under consideration.
”The issue of military intervention, which is also always complex, is not right now on the table when it comes to Syria,” he said.
Russia and China, which have both blocked previous attempts at the Security Council to condemn Assad, joined other council members on Sunday in approving a statement condemning the Houla massacre.
But Russia insists that that rebuke went far enough and that further action would be counter-productive.
President Vladimir Putin’s spokesman said that stance would not change under pressure.
”Russia’s position is well-known. It is balanced and consistent,” Interfax quoted spokesman Dmitry Peskov as saying on Thursday. ”So it is hardly appropriate to talk about this position changing under someone’s pressure.”
On the ground, Syrian forces resumed shelling in Houla, which had begun on Wednesday, with a young boy killed by a sniper, the Observatory said.
And battles raged as troops and rebels clashed across the country, with the Observatory saying at least 13 other people were killed. – Sapa-AFP