Security forces deployed in strength -- as on every Friday over the past 10 months for the main weekly protests -- killed at least 10 people including a six-year-old girl, the Syrian Observatory for Human Rights said.
It said five people were killed in Homs, one in Hama, two in Damir near the capital, including the little girl, and two more in Idlib province and the Aleppo region.
Burhan Ghaliun, head of the Syrian National Council, an umbrella group that initially opposed the use of force in the uprising, met on Thursday with rebel army chief Colonel Riad al-Asaad.
They agreed to "formulate a detailed plan, to include the reorganisation of FSA units and brigades, and the creation of a format to accommodate within FSA ranks additional officers and soldiers, especially senior military officials, who side with the revolution," the SNC said.
Formed from deserters from the regular army who mutinied over the regime's deadly crackdown, the FSA says it has some 40,000 fighters under its command.
UN chief Ban Ki-moon, who was in neighbouring Lebanon on Friday, called for the world to stand together to address a crisis that the world body estimates has cost more than 5,000 lives.
In an interview with Lebanon's An-Nahar daily, Ban said he had repeatedly appealed to Assad to stop the bloodshed and listen to his people but that he had received only empty promises.
He said the Security Council must speak with one voice in seeking an end to the crisis, but Moscow renewed its opposition to Western calls for tougher action by the world body.
In October, Russia and China vetoed a draft resolution that would have condemned the Assad regime. Russia later offered an alternative that would single out the opposition for criticism as well.
Russian Deputy Foreign Minister Gennady Gatilov rejected on Friday Western-proposed amendments to that draft.
"Unfortunately, the West's approach radically differs from ours," Gatilov said. "Judging by the contents of their proposed amendments, their goal is clearly aimed at removing Assad's regime in Damascus."
And Dmitry Rogozin, Moscow's departing ambassador to NATO, warned the West against any foreign intervention in Syria. "You shouldn't interfere in Syrian affairs. This is very dangerous," he told reporters in Brussels.
Cameron, who was in Saudi Arabia for talks with King Abdullah on regional tensions, told Al-Arabiya television that Britain stands ready to take a fresh resolution on Syria to the Security Council.
The step would dare "others that if they want to veto that resolution to try to explain why they are willing to stand by and watch appalling bloodshed by someone who has turned into such an appalling dictator," he said.
"This is appalling bloodshed, appalling murder on the streets of Syria. The whole Arab League has come together and said it's unacceptable and others need to listen to that and act on that at the UN."
The opposition has called for the Arab League to pull its observers out of Syria or at least seek UN tactical support, saying they have been ineffective in ending the violence and repeatedly duped by the authorities.
But the League said observers would see the mission through until its initial one-month term finishes on January 19.
An Arab League deal signed with Damascus called for an end to violence against civilians, the withdrawal of the military from cities, the release of detainees and free access for foreign media.
Meanwhile, a Russian ship carrying "dangerous cargo" has sailed for Syria after a stopover in Cyprus, despite a pledge given to Cypriot authorities not to travel on to the unrest-swept state, its owner said on Friday.
An independent Russian military analyst said the ship was likely to dock at the Syrian port of Tartus with what media said may be up to 60 tonnes of ammunition supplied by the state Russian arms exporter.
In Washington, State Department spokeswoman Victoria Nuland said the United States had raised concerns with Russia and Cyprus over the ship.
"With regard to the ship, we have raised our concerns about this, both with Russia and with Cyprus, which was the last port of call for the ship," she said.
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