A vigil in Amman, Jordan, to mark the Syrian anniversary
As Syrians mark the second anniversary of the start of the nation's unrest, the EU is set to discuss lifting its arms embargo to allow supplying rebels.
The leaders of France and Britain will try to push other EU members to agree to the move at the Brussels summit.
Ties with Russia, one of Syria's key allies and which strongly opposes arming rebels, will also be discussed.
Up to 70,000 people have been killed in Syria since the uprising against President Bashar al-Assad began.
About one million people have fled the country.
The unrest began on 15 March 2011 with nationwide protests following arrests in the southern city of Daraa.
Rebels now control large sections of Syria, but the conflict has appeared to be largely in stalemate for months.
A number of vigils have already been held around the world to mark the second anniversary of the conflict, including in the South Korean capital, Seoul, and in Amman in Jordan, where children gathered in front of the Citadel for an event organised by Save the Children.
Jordanian student Aya Khirfan said: "We are here to deliver a very important message to help the people and the children of Syria. We are all there for them and this conflict in Syria will someday be solved."
French President Francois Hollande and UK Prime Minister David Cameron are expected on Friday to raise the issue of the arms embargo at the talks in Brussels, although Syria is not a formal agenda item.
Speaking on Thursday, Mr Hollande said that Paris was "ready to support the rebels".
"We cannot allow the massacre of a people by a regime which right now does not want a political transition.
"France's view is that arms are being delivered to Syria - but to the regime of Bashar, in particular by the Russians," he said.
But the French president stressed that his aim was not a "total war".
A British official said there was a "perversity" about the embargo.
"The embargo does not stop those aiding Assad, but it does stop those who want to help the opposition," the official said.
The UK has indicated that it might veto a forthcoming vote, due in May, to extend the embargo, and Mr Cameron has said that it is "not out of the question we may have to do things in our own way".
The French view, largely shared by London, is that Russia and also Iran are arming government forces, and providing weapons to the opposition is the only way to put pressure on the Assad regime, the BBC's Chris Morris reports from Brussels.
US state department spokeswoman Victoria Nuland said Washington did not want to "get in the middle of their internal discussions, but we certainly want to see as many governments as possible provide appropriate support to the Syrian opposition coalition".
Germany, Austria and Sweden are among the EU states believed to be reluctant to lift the embargo, our correspondent says.
There is also concern in many countries that pouring more weapons into Syria could escalate the conflict.
The UN's Under-Secretary General for Humanitarian Affairs, Valerie Amos, said the move could make the job of humanitarian agencies "more difficult".
And Russia on Thursday restated its explicit opposition, with Foreign Minister Sergei Lavrov saying that "arming the opposition is not an option".
There is also concern at the UN that Lebanon is becoming more entangled in the conflict.
A UN Security Council statement underscored its concern about cross border attacks and weapons trafficking between Lebanon and Syria.
The BBC's Barbara Plett, at the UN, says Western governments believe the Hezbollah militant group is increasing its support for the Syrian government.
She says diplomats also believe Iran has accelerated its weapons supply to Syria to try to tip the balance in favour of the Assad government.
As Syria heads into its third year of conflict, opposition forces will meet in Istanbul on Monday with the aim of naming a prime minister who can oversee the formation of an interim government.
Walid al-Bunni, a spokesman for the main opposition, the Western-backed Syrian National Coalition, said: "We are in desperate need for an interim government, a recognised civilian entity that can restore law and order and secure basic services to liberated areas."
Meanwhile, violence continued across the country on Thursday, with activists reporting that government forces had bombarded several areas, including the western city of Homs, following a recent rebel offensive there.