The deliveries, in two shipments this month to the northern Syrian port of Latakia totaled 4.1 percent of the roughly 1433 metric tons of toxic agents reported by Damascus to the Organization for the Prohibition of Chemical Weapons (OPCW), said the sources, who spoke on condition of anonymity.

“It’s not enough and there is no sign of more,” one source briefed on the situation said.

The internationally backed operation, overseen by a joint OPCW-United Nations mission, is now 6-8 weeks behind schedule. Damascus needs to show it is still serious about relinquishing its chemical weapons, the sources told Reuters.