The British deputy representative to the Organisation for the Prohibition of Chemical Weapons (OPCW) told delegates in The Hague that packaging material had arrived for the 100 metric tonnes of toxic chemicals.
"But there is still no sign of any movement of chemicals, nor any indications of a time scale for a move," said the statement, a copy of which was obtained by Reuters.
Syrian President Bashar al-Assad, embroiled in civil war with rebels fighting to oust him, agreed last year to hand over the country's entire chemical weapons stockpile after hundreds of people were killed in a sarin gas attack near Damascus.
The agreement with Russia and the United States averted Western military strikes threatened in response to the worst chemical weapons atrocity in decades, which has been blamed by Washington on Assad's government.
His government, which denies the allegation and blames the rebels, still has roughly 7 percent of 1,300 tonnes it declared to the OPCW, enough highly toxic material to carry out a large-scale attack.
It has missed several deadlines, most recently its own promise to hand over the remaining chemicals by April 27. It has also failed to destroy a dozen facilities that were part of the chemical weapons programme.
Under the deal, Syria's entire stockpile is supposed to have been destroyed by mid-2014, but "it is growing ever clearer that the 30 June deadline will not be met", the British statement said.
PACKED FOR SHIPMENT
There was confusion earlier this week about how much progress there had been in transporting the remaining chemicals to the Syrian port of Latakia, from where they will be shipped overseas for destruction.
The Pentagon said on Tuesday "it is starting to be moved as we speak," and senior diplomats from two other Security Council member states told reporters on Wednesday there were indications the Syrians were preparing to dispatch the remaining stockpile.
A diplomat in the Middle East said the remaining chemicals have been packed in containers, but that the joint U.N.-OPCW operation overseeing the destruction still lacks access to the site.
The Syrian army has launched a military operation in the area, where the chemical storage site is being monitored remotely by camera, to clear the way for transport of the toxins, the source, who spoke on condition of anonymity, said.
The operation to destroy Syria's chemical stockpile is a complex logistical undertaking, involving a dozen countries and hundreds of millions of dollars.
The most toxic chemicals are to be destroyed onboard the Cape Ray, a converted U.S. cargo ship, after being dropped off by Norwegian and Danish vessels now waiting in the Mediterranean.
The remaining bulk chemicals are to go to commercial destruction facilities in Britain, Finland and Germany.