The United Nations says almost half of all Syrians have now been forced to abandon their homes, as the number of those affected by the conflict continues to rise.
Three million refugees are now registered in neighbouring countries while the number of people displaced within Syria has risen to 6.5 million.
Hundreds of thousands more remain unaccounted for. The rapidly deteriorating situation prompted the UN High Commissioner for Refugees, Antonio Guterres, to describe the crisis as the "biggest humanitarian emergency of our era", adding, "…the world is failing to meet the needs of refugees, or countries hosting them."
The US has been reluctant to take military action in Syria, but President Barack Obama has recently authorised so-called reconnaissance flights over Syria. It is understood they will involve drones and piloted aircraft.
But will they pave the way for an expansion of the aerial campaign being carried out by the US against the Islamic State group in Iraq?
Presenter: Sohail Rahman
Melissa Fleming - spokesperson for the UN Refugee Agency, UNHCR.
Sajjan Gohel - Director of International Security at the Asia-Pacific Foundation.
Mahjoob Zweiri - professor of contemporary history of the Middle East at Qatar University.