The world's chemical weapons watchdog is pressing Syria to explain why it has four undeclared warfare agents, its head said Wednesday, after a U.S. official accused Damascus of continuing to hoard a toxic stockpile.

Organization for the Prohibition of Chemical Weapons chief Ahmet Uzumcu said despite previous declarations by Syria, OPCW teams have found indications of five additional chemical agents.

The OPCW chief added that "new information" offered by Damascus has failed to resolve outstanding issues on Syria's chemical warfare program.

- Syria 'cynically' exploiting pact --

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