The global chemical weapons watchdog says security "challenges" in Syria slowed the transport of raw materials for poison gas and nerve agents to a port for transport and eventual destruction, but additional measures are being taken and the process should pick up in the coming days and weeks.

The head of the Organization for the Prohibition of Chemical Weapons, Ahmet Uzumcu, said Thursday he is still confident that Syria's chemical weapons will be destroyed as scheduled by the end of June.

In a briefing with reporters, Uzumcu said the OPCW met with Syrian officials in the Hague on Wednesday to discuss the delays. He said additional measures are being taken and "we hope we can move relatively quickly in the coming weeks."