European Union foreign ministers are discussing British and French calls for an easing of sanctions against Syria so weapons can be supplied to the rebels.
France and the UK are expected to argue that the move would increase pressure on Damascus for a political solution.
However, several EU states are totally opposed to ending the arms embargo, which expires on 31 May.
EU officials have warned against jeopardising a current initiative to hold an international peace conference.
Syria’s foreign minister confirmed on Sunday that the government would “in principle” attend the conference which the US and Russia hope will take place in Geneva next month.
Walid Muallem said it would be “a good opportunity for a political solution” to the conflict, which the UN says has left more than 80,000 people dead.
In a conflict which worsens by the week, this is a week when critical decisions on the next steps in Syria must be made.
The US Secretary of State, John Kerry, has added his voice to those urging Europe to ease restrictions on military support for the opposition. “Fine for him to say but what is Washington willing to do?” one European foreign minister opposed to lifting the ban told me.
On Monday, Mr Kerry meets his Russian counterpart, Sergei Lavrov, in Paris. Their talks are expected to focus on plans for the first conference to bring together representatives of the Syrian government and opposition.
The meetings in Brussels and Paris are linked.
One of the main concerns in many European capitals is the impact any lifting or easing of the EU arms embargo might have on the fragile effort to fashion a political transition.
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Members of the main opposition coalition are currently discussing whether to attend the conference, but spokesmen have said they would if President Bashar al-Assa
Foreign Secretary William Hague has said the UK has decided to recognise the Syrian opposition coalition.
He told MPs the National Coalition of the Syrian Revolutionary and Opposition Forces was the “sole legitimate representative” of the Syrian people.
He said they were now a “credible” alternative to the Assad government.
In the absence of a diplomatic solution, he told MPs the UK would not rule out any action - subject to international law - to save lives.
Up to 30,000 people have been killed in the 18-month conflict, the UK believes.
Those trying to bring down President Bashar al-Assad’s government moved closer to a united front when the rival leaders of Syria’s rebels formed the coalition after months of bitter division.
Syrian rebels have been accused of possibly committing a war crime after a video allegedly showing an execution of government soldiers appeared online.
The UN and Amnesty International condemned the alleged killings which reportedly took place after the rebels seized army checkpoints on Thursday.
Footage apparently shows the rebels beating soldiers before shooting them.
Unconfirmed reports say troops have now quit all bases near the strategic northern town of Saraqeb.
The town lies near both the main Damascus-Aleppo highway and the highway linking Aleppo to the coastal city of Latakia - making it doubly strategic.
The army, meanwhile, continued its air strikes across Syria on Thursday.
In all, more than 150 people reportedly died in fighting, said the Syrian Observatory for Human Rights (SOHR), a UK-based activist group.
After artillery exchanges between Turkey and Syria, Ankara is preparing for conflict and at the same time stating it does not intend to declare war. The West has responded slowly to play down the clash’s importance.
Over the last few weeks Turkish troops on the border with Syria have observed and noted the movements of Syrian artillery units across the border near Akcakale in southwest Anatolia. Using these observations, the military and politicians in Ankara were able say where the deadly grenades had been fired from just a few hours after an attack on a Turkish border town occurred on Wednesday. Turkish officials were also convinced the shots were intentionally fired.
In response, Turkish howitzers targeted a Syrian unit that had been located by radar and which, according to reports, was located anywhere from three kilometers to 30 kilometers into Syrian territory.
Spark before the flame?
Turkey is not limiting its response to howitzer fire. The air force and navy were put on alert, according to press reports. On Thursday, Turkey renewed its retaliatory shots at Syria.
Few doubts remain about Turkey’s resolve to consider a full military reaction against Syria. The Turkish parliament set to meet Thursday morning for an emergency session and give their blessing for potential deployment in Syria. A regional surface war as a result of unrest in Syria could now, as German Foreign Minister Guido Westerwelle has warned for months, become a realistic scenario, though an aide to Turkish Prime Minister Prime Minister Recep Tayyip Erdogan told reporters Thursday that Turkey did not intend to declare war on Syria.
More than 20,000 Syrian troops are massed around Aleppo, military sources say, as fighting rages for control of the country’s second city.
Fighter jets, helicopters and artillery have pounded rebel positions ahead of a feared full-scale assault within days.
In Damascus, another key battleground in the war, army sources said rebels had been pushed from a last stronghold. The rebels said they had withdrawn.
Meanwhile, Iran is seeking the release of 48 Iranians kidnapped on Saturday.
Iranian diplomats and Syrian state television blamed the abduction, which took place near the shrine of Sayyida Zainab in a suburb of Damascus, on “armed groups”.
The U.N. General Assembly overwhelmingly passed a resolution Friday criticizing the Security Council’s failure to act on the Syria conflict, which U.N. leader Ban Ki-moon said has become a “proxy war”.
The resolution, which condemned President Bashar Assad’s use of “heavy weapons” in his battle against the rebellion against his rule, was passed by 133 votes with 12 countries against and 31 abstaining.
Russia and China, which have vetoed three U.N. Security Council resolutions on Syria, were among high profile opponents of the resolution.
Many diplomats said Friday’s vote was a show of frustration and anger at the lack of international action on the conflict.
Though the resolution is not legally binding, there was increased attention on the General Assembly action after the resignation of U.N.-Arab League envoy Kofi Annan and the mounting battle for the Syrian city of Aleppo.
The resolution said members deplored “the Security Council failure to agree on measures” to make the Syrian government carry out U.N. demands to end almost 18 months of fighting.
The Syrian capital Damascus has seen some of the heaviest fighting of the conflict so far, according to reports from activists and residents.
Plumes of smoke were seen rising from the suburbs as the army sought to drive out the Free Syrian Army.
The fighting comes after the International Committee of the Red Cross (ICRC) said the conflict in Syria was now in effect a civil war.
It means combatants across Syria are now subject to the Geneva Conventions.
It had previously regarded only the areas around Idlib, Homs and Hama as warzones.
The BBC’s Jim Muir says the clashes between government forces and Free Syrian Army rebels seem to be creeping ever closer to the heart of Damascus and the centre of the regime’s power.
Tanks and mortars were reportedly used on the southern edge of the city, in areas like Tadhamon and Midan and around nearby Palestinian refugee camps.
Residents were said to be fleeing some areas, while in other parts of the city protesters blocked motorways with burning tyres.
On either side of Syria Street, battered buildings house hidden arsenals and legions of angry young men primed to confront their enemies across the road. Edgy lookouts on motorbikes make regular rounds, carrying walkie-talkies and ready to call out the reinforcements if needed.
“We are vigilant. We are lions,” said an enforcer from the Jabal Mohsen neighborhood that rises up a hill from Syria Street, a muscular man in his 30s with watchful eyes and a two-way radio. “If they attack us, then … ” His voice trailed off as he made a swift motion as if slitting a throat.
Throughout the neighborhood of shambolic cafes below the bullet-scarred facades of concrete apartment blocks, outsize posters of “Doctor Bashar” — Syrian President Bashar Assad — rally residents, mostly members of Assad’s minority Alawite sect.
Down the hill, in the equally frayed streets of the Bab Tabbaneh district, which, like the rest of the city, is predominantly Sunni Muslim, just the mention of the Syrian leader’s name unleashes a slew of epithets: child killer, torturer, tyrant.
This is not war-ravaged Syria, but Lebanon’s second-largest city, Tripoli.
As the conflict in Syria lurches toward all-out civil war, diplomats voice grave concern about “spillover” to neighboring nations, notably Lebanon, where memories of a long, traumatic civil war and the Syrian army’s occupation of the country remain fresh.
But here in Tripoli — more specifically in the volatile districts of Jabal Mohsen and Bab Tabbaneh, divided by the aptly named Syria Street — the “contagion” from Syria has already arrived, and it’s toxic.