A coalition of Western and Middle East powers warned on Thursday that they would seek tougher international action if Bashar al-Assad's Syrian regime continues to flout a shaky UN peace plan.
Senior officials, including US Secretary of State Hillary Clinton and French Foreign Minister Alain Juppe, accused Assad of breaking the ceasefire and said a UN observer mission would have to be dramatically reinforced.
And Clinton called on the international community to press the UN Security Council to authorise a so-called Chapter Seven resolution, which would brand Assad a threat to peace and authorise tough international measures.
These could include, she said, "travel and financial sanctions, an arms embargo, and the pressure that that will give us on the regime to push for compliance with Kofi Annan's six-point plan".
Clinton also raised the prospect that Turkey could react to "outrageous" Syrian shelling on its border by invoking a clause in the NATO alliance treaty that would require members to decide if their security is threatened.
Juppe warned that Syria was on course for "civil war" and confirmed the 15 nations present had agreed to seek "other options" if the Annan plan fails.
Earlier, Juppe's leader President Nicolas Sarkozy had spoken of the possibility of setting "humanitarian corridors" in a country where 11,000 have died in the year since Assad launched a crackdown on a popular revolt.
The Paris meeting included foreign ministers and envoys from Germany, Saudi Arabia, Canada, Egypt, the UAE, Spain, the United States, Italy, Jordan, Kuwait, Morocco, Qatar, Britain, Tunisia, Turkey and the European Union.
But there were notable absentees, including Russian Foreign Minister Sergei Lavrov, whose government wields a veto at the Security Council and would be likely to block any attempt to seek a Chapter Seven resolution.
"We need to start moving very vigorously in the Security Council for a Chapter Seven sanctions resolution," Clinton told the envoys.
"Now, I'm well aware that at this point such an effort is still likely to be vetoed, but we need to look for a way to keep pressing forward," she said, adding she had earlier met her Russian counterpart Lavrov in Brussels.
"He was, as usual, very intent upon laying responsibility on all sides, and in particular on the opposition, but he also has recognised that we are not in a static situation but a deteriorating one," she said.
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Saudi Foreign Minister Prince Saud al-Faisal took an indirect swipe at Russia's refusal to stop supplying arms to Damascus, saying: "I'm surprised that the oppressing regime can continue to arm itself while the innocent victims don't have the means to defend themselves."
Earlier, Juppe had insisted: "The Annan plan is a chance for peace, a chance that should not be missed."
"The opposition has fulfilled its obligations under the Annan plan, which was welcomed by the Syrian National Council," he said, referring to the main umbrella body representing the diverse anti-regime forces.
"The Syrian regime... is pursuing without shame repressive tactics that have already left dozens more dead since the ceasefire was due to go into effect," he said.
He called for tough sanctions against Damascus and for the small UN observer team on the ground to be boosted to 300 or 400-strong and made "robust and credible" by being given land and air transport to cover the country.
"The Security Council will have to adopt a new resolution to set up an observer mission," Juppe said.
"We feel this must have a mandate and the necessary means to achieve its objectives. France and its partners on the Security Council will very quickly propose a draft resolution."
Earlier, Lavrov had insisted that Moscow was "honestly fulfilling its part" in efforts to end the violence and said the international community should stop predicting that Annan's peace plan would fail.
"I have today called on my colleagues to abandon the rhetoric of self-fulfilling prophecies," Lavrov said in Brussels.
"Before thinking about what to do in the future, we should do everything to make this plan successful."
Meanwhile, there have been reports of fresh violence in Syria, where the UN says over 9,000 people have died in the past 13 months of fighting. Rights groups and Juppe, speaking for the coalition, claim 11,000.
Syrian troops have continued to pound rebel strongholds, including the city of Homs, even while the regime sought to reassure an increasingly sceptical world that it is committed to a week-old ceasefire.