(CBS/AP) PARIS - France took a tougher line in negotiations over Syria on Thursday, with French President Nicolas Sarkozy calling Syrian President Bashar Assad a "liar," while the French foreign minister urged a more robust international observer mission than Damascus has been willing to accept.
They spoke as Paris hosted a dozen top diplomats from the U.S., Europe and Arab states in the so-called "Friends of Syria" group to look for ways of helping special envoy Kofi Annan's peace plan to end the violence in the country. The group called Annan's plan the "last hope" to resolve the crisis, according to Reuters.
At the meeting, U.S. Secretary of State Hillary Rodham Clinton called for a new U.N. resolution authorizing an arms embargo and other stronger measures on Syria if it fails to abide by U.N.-backed cease-fire.
Clinton stopped short of calling for outside military intervention in Syria but said the time has come to impose more consequential measures.
U.N. Secretary-General Ban Ki-moon said earlier Thursday that Syria was, which took effect last week, and that violence was escalating in the Arab country.
Secretary-General Ban Ki-moon demanded Syria immediately pull its troops and heavy military equipment out of cities and towns.
Any attempt to push for U.N. sanctions on Syria could meet resistance from Russia and China, which hold vetoes on the U.N. Security Council.
In Syria on Thursday, activists said regime forces took control of a southern town and shot at activists in another soon after international observers left. Protesters chanted anti-government slogans for the observers to hear.
French Foreign Minister Alain Juppe said an effective force of U.N.-backed observers for Syria would require 300 to 400 well-equipped monitors to help end 13 months of bloody repression in the country.
Syrian President Bashar Assad's regime says it will accept no more than 250 observers, while the the U.N. Secretary-General has asked for 300 to be sent in. Only a small advance team of seven is on the ground now.
Juppe said two main questions will be on the table at the Paris meeting, attended by Arab countries including Saudi Arabia, U.N. Security Council member Morocco and Qatar, plus Western powers such as the U.S., Britain and Germany.
"Can we contribute to the deployment of a real force of effective observers on the ground, in other words that they are numerous at least 300-400 observers to cover the country that they are well-equipped, with some robust missions, and have the means to get around the country," Juppe said.
"And if that's not possible within a certain time frame, what other measures and initiatives must be taken to stop the massacre?" he said.
But even as France ramped up its rhetoric on Syria President Nicolas Sarkozy called Assad a "liar" Thursday the U.S. and other allies appear ready to leave the Syrian president where he is, if only because the alternatives are so limited.
France and the United States and others have repeatedly called for Assad to step aside. But the Obama administration's policy now reflects a consensus that Assad with support from the military has a strong hold on power and only an outside military strike could quickly oust him.
Western powers have not advocated a foreign military intervention, though some Arab states have pledged financing for the rebels to help pay for weapons, promises that have yet to turn into cash.
The evolving U.S. position comes amid signs that rebel forces are poorly armed and disorganized, efforts to pay them by Arab Gulf states are failing, and sectarian divisions loom in Syria.
Still, top U.S. military officials said the U.S. is working on additional ways to try to halt the unending violence in Syria.
Defense Secretary Leon Panetta and Army Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, outlined the steps the United States is taking to pressure the regime of President Bashar Assad, including direct non-lethal support to the opposition such as communications equipment and emergency humanitarian assistance of $25 million. But the two made clear that unilateral military action is far from a solution.
"There is no silver bullet," Panetta told the House Armed Services Committee Thursday. "At the same time, the situation is of grave consequence to the Syrian people."
Russia, an ally of Syria, has criticized the "Friends of Syria" group and insisted that only the U.N. can assess whether Annan's cease-fire plan was being carried out. Lavrov said Wednesday that Russia worried about efforts to "privatize" the Annan plan.
Juppe said he had personally invited Russian Foreign Minister Sergey Lavrov but was rejected: "I regret that Russia continues to close itself off in a vision that isolates it not only from the Arab world but the international community."
Russia, along with China, has twice shielded Syria from U.N. sanctions over its yearlong, deadly crackdown on a popular uprising. But Moscow has strongly supported the Annan plan, which aims to end the violence that is estimated to have killed more than 9,000 people so far.
France's Foreign Ministry tweeted Thursday that China also had been invited for the Paris meeting but had declined.
Meanwhile, in Geneva, Annan said Syria's government and the United Nations have agreed on rules governing the U.N.'s advance team of truce monitors.
The agreement covers how the team of up to 30 observers will "monitor and support a cessation of armed violence in all its forms by all parties" and implement Annan's six-point peace plan, Annan spokesman Ahmad Fawzi said in a statement.
The deal also outlines the "tasks and responsibilities" of the Syrian government, he added.
On Thursday, the observers visited the southern province of Daraa, where activists said anti-regime protesters gathered around them in the village of Khirbet Ghazaleh. The state-run news agency confirmed the observers went to Daraa.
An amateur video posted online by activists showed at least two of the observers, including the team's head Col. Ahmed Himiche, standing outside a U.N. vehicle as dozens of people chanted "death is better than humiliation" and "the people want to topple the regime."
Troops also stormed and took control of the southern town of Busra al-Harir, which regime forces have been attacking for about a month, the Local Coordination Committees activist group said.
Adel al-Omari, an activist based near Busra al-Harir, said the whole town fell in the hand of regime forces Wednesday night after army defectors withdrew from the area.
"Forty percent of Busra al-Harir's homes are destroyed because of the shelling," he said, adding that regime forces are detaining many in the town. "There is a lack of medical products, and regime forces have taken over makeshift hospitals."
Al-Omari said that as observers were visiting the village of Hirak, hundreds of protesters chanted for the downfall of Assad's regime.
"Once the observers left, security forces started shooting to disperse the demonstration," al-Omari said, adding that at least three protesters were wounded.
The Local Coordination Committees said troops opened fire in the Mahata area in the southern city of Daraa, apparently to impose a curfew. It said at least 10 civilians were wounded in the shooting.
A U.N.-backed survey released Thursday has found that the number of civilians uprooted inside Syria has jumped by some 230,000 since the start of the uprising last year.
The report by the Norwegian Refugees Council and the Geneva-based Internal Displacement Monitoring Center says over 600,000 people are now internally displaced inside Syria, including some 400,000 from the country's 1967 war with Israel.
Tens of thousands more have fled to neighboring countries.