AMSTERDAM — The United States has stepped forward to help destroy some of the most lethal parts of Syria’s chemical weapons stockpile at an offshore facility, the Organization for the Prohibition of Chemical weapons said Saturday.

The international organization’s director-general, Ahmet Uzumcu, said the U.S. government will contribute “a destruction technology, full operational support and financing to neutralize” the weapons offshore, most likely on a ship in the Mediterranean Sea. The weapons are to be removed from Syria by Dec. 31.

The OPCW also wants nearly 800 tons of chemicals, many of which are industrial chemicals regularly destroyed at civilian facilities all over the world, to be destroyed by private companies as part of the organization’s ambitious plan to completely eradicate Syria’s chemical weapons program by mid-2014.

The OPCW was charged with overseeing the destruction of Syria’s chemical weapons arsenal under an agreement reached between the U.S. and Syrian ally Russia on Sept. 14. The U.S. then shelved plans for a military strike on Syria as punishment for a chemical attack on Damascus on Aug. 21 that killed more than a thousand civilians.