EU foreign policy chief Catheron Ashton urged caution amid a drive by France and Britain to lift an EU arms embargo on Syria in an attempt to aid the rebels fighting President Bashar al-Assad.

Ashton on Saturday said the EU needed to be "very carefully" about lifting the embargo, saying, "What we've got to make sure of is anything we do does not make that (work) harder."

"Would putting weapons into the field make it more or less likely that others will do the same? What would be the response of Assad based on what we know about his response so far? Would it stop people being killed or would it kill people faster?" she added.

Ashton also suggested that EU officials consult U.N. mediator Lakhdar Brahimi and head of the opposition Syrian National Coalition, Moaz al-Khatib, about the impact the lifting of the ban might have on the crisis.