The United States will destroy the most dangerous of Syria’s chemical weapon stockpile on a ship at sea.

The United States will destroy the most dangerous of Syria's chemical weapon stockpile on a ship at sea, the world's chemical watchdog said on Saturday.

"The neutralization operations will be conducted on a US vessel at sea using hydrolysis," the Organization for the Prohibition of Chemical Weapons said in a statement.

"Currently a suitable naval vessel is undergoing modifications to support the operations and to accommodate verification activities by the OPCW," The Hague-based watchdog added.

The ship operation will destroy what is known as "priority chemical weapons", the most dangerous of Syria's total arsenal and ones that have to be out of the country by December 31 under an international deal agreed to avert military strikes on Damascus.

OPCW spokesman Michael Luhan on Saturday declined to name the navy vessel to be used.

A final plan for the destruction of Syria's chemical weapons -- on land or at sea -- is due to be approved by December 17.

Sigrid Kaag, the top UN official from the joint UN-OPCW mission, confirmed the use of a US ship to render Syria's chemical weapons stating that it "will not be in Syrian territorial waters."