The United States has offered to destroy Syria's chemical weapons on an American ship, and is looking for a suitable Mediterranean port where the operation can be carried out, the world's chemical weapons watchdog has said.

The Netherlands-based Organisation for the Prohibition of Chemical Weapons (OPCW) said on Saturday that the weapons would be destroyed on a US vessel at sea using hydrolysis, and that a ship was already undergoing modifications to carry out the operation.

OPCW's director-general Ahmet Uzumcu said that the US government will contribute ``a destruction technology, full operational support and financing to neutralise'' the weapons, most likely on a ship in the Mediterranean Sea.

The operation would destroy 500 tonnes of Syria's most dangerous chemical weapons, including nerve agents, which are considered too dangerous to import into a country or process commercially.

Known as "priority chemical weapons", these weapons have to be out of Syria by December 31 under an international deal agreed to avert military strikes on Damascus.

Separately, the woman appointed as go-between for the United Nations and the OPCW on destroying Syria's chemical weapons stockpile laid out some logistical details.

Sigrid Kaag said the weapons will first be sealed and packaged and then transported from multiple sites within Syria to the country's largest port, Latakia. 

Then they will be loaded onto ships owned by other OPCW members before a second hand-off to US vessels.

The weapons and chemicals "will not be (destroyed) in Syrian territorial waters,'' Kaag said at a news conference in Damascus.

Kaag, who is due to travel to The Hague by Monday, said the mission will require international contributions in terms of packaging material, other logistic needs and special equipment needed to get the job done.

Earlier this month, the OPCW adopted a final roadmap for ridding Syria of more than 1,000 tonnes of dangerous chemicals by mid-2014.

Source: Agencies