Syria will miss a major deadline next week in the programme to destroy its chemical weapons production facilities, sources at the Organisation for the Prohibition of Chemical Weapons said last night.

Syria declared 12 production facilities to the OPCW and has until 15 March to destroy them under a deal agreed with the United States and Russia.

The Syrian regime has already missed several deadlines laid out in the agreement.

"That will definitely be missed," said an official involved in discussions with Syria, referring to the 15 March deadline.

The official, who asked not to be identified, said there were seven "hardened" aircraft hangars and five underground facilities.

"None of them have been destroyed at the moment," the official said.

Syrian officials could not immediately be reached for comment.

The regime agreed last year to destroy all chemical weapons facilities and surrender 1,300 metric tonnes of toxic agents to a joint OPCW/United Nations mission.

It has until 30 June to eliminate its chemical weapons programme completely.

The deal averted US missile strikes threatened by the US after a 21 August sarin gas attack killed hundreds of people in the outskirts of the capital.

Syria missed a 5 February deadline to ship all chemicals abroad for destruction and is weeks behind schedule.

It has increased the handover of poisonous agents, including a shipment of mustard gas this week, but will not meet a 30 March deadline to neutralise all the chemicals overseas, sources at OPCW said.

That process was already supposed to have started on board the US MV Cape Ray, a cargo ship outfitted with special chemical neutralisation equipment.

But only a quarter of the priority one chemicals, the most dangerous ingredients for chemical weapons, have been relinquished, officials said.

Syria is not taking the deadline for the destruction of production facilities seriously, another source at the OPCW said last night.

"They are not doing things in the timeframe they promised they would," the source said. "The process is in volatile waters."