"The Syrian government has completed the delivery of the 13th consignment of chemicals," the Organisation for the Prohibition of Chemical Weapons (OPCW) said.
"The deliveries have raised the overall portion of chemicals removed from Syria to 65.1 per cent, including 57.4 per cent of priority chemicals," it reported in a statement in The Hague.
Damascus had temporarily halted the transfer of its chemical stockpile, citing security reasons, but resumed the operations earlier this month.
The agreement was reached after deadly chemical attacks outside Damascus last August that the West blamed on President Bashar al-Assad's regime.
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Sigrid Kaag, who coordinates a combined UN-OPCW mission in Syria to oversee the transfer, told the UN Security Council on April 3 that Damascus could still make the June 30 cut-off.
But she warned any delay would make it "increasingly challenging" to stick to the deadline, diplomats in New York said.
In a statement, he said "both the frequency and the volumes of deliveries have to increase significantly" if the transfers are to be finished "against the projected time frame".
Norwegian as well as Danish naval vessels are involved in the process of removing the materials from the port of Latakia in western Syria, the most dangerous of which are to be transferred to a US Navy vessel specially fitted with equipment to destroy them at sea.