Shifting battlefronts between Syrian forces and foreign-backed insurgents as well as severe weather conditions have delayed the delivery of essential materials to sites where the toxins are being prepared for shipment to Latakia Port, OPCW said.
"A delay will probably occur," Franz Krawinkler, the OPCW's logistics head stated on Saturday.
"Because of various external influences, including the weather... certain logistical supplies that are needed for this transport, could not be delivered in time," Krawinkler added.
A Russian diplomat was also quoted as saying on Friday that the deadline would be missed because the toxins still faced a potentially hazardous transport to Latakia.
"The removal has not yet begun," Russia's head of the Foreign Ministry's disarmament department Mikhail Ulyanov said.
"They will have to be taken on dangerous roads; there are several dangerous stretches," Ulyanov added.
The OPCW mission to remove chemical arms from Syria was established under a UN resolution passed after agreement between Russia and the US.
The resolution followed international outrage over an alleged chemical weapons attack near Damascus in August.
The foreign-sponsored Syrian opposition forces where widely suspected to be behind the carnage, estimated to have killed hundreds of people, although the US-led alliance of Western and regional countries tried to put the blame on Damascus largely through unverified media reports.
RA/MB