United Nations chemical weapons experts prepare before collecting samples from one of the sites of an alleged chemical weapons attack in Damascus' suburb of Zamalka on August 29, 2013. File picture: Bassam Khabieh

The Hague - The global chemical arms watchdog said on Friday that it has chosen two US and Finnish companies to help destroy Syria's chemical arsenal as part of an ambitious plan that has suffered a string of setbacks.

The Organisation for the Prohibition of Chemical Weapons (OPCW) said Finland's Ekokem would destroy chemical weapon ingredients as well as some effluent left over from destruction activities aboard a US ship.

The US subsidiary of French company Veolia Environment was chosen from 14 bids from around the world to destroy the remainder of the chemicals, the OPCW said in a statement.

“The conclusion of this process represents an important step towards the full destruction of Syrian chemical weapons within the agreed timelines,” it added, amid Western accusations that Damascus is dragging its feet.

Syria's chemical arms and precursors are slowly leaving the country on Western warships, from where they will be transferred to the US ship to be turned into toxic sludge or to companies that have agreed to destroy the other chemicals.

Tenders to help destroy Syria's entire arsenal by a tight June 30 deadline came from a wide range of companies, including France's Airbus, China National Chemical Corporation, Switzerland's Dottikon and US-based Paragon Waste Solutions.

Germany said in January that it would help destroy waste left over from neutralising Syria's chemicals, and Britain said in December it would destroy 150 tons of its industrial grade chemicals.

The OPCW and the United Nations are participating in a joint mission overseeing the destruction of Syria's chemical weapons programme under a UN resolution approved last year.

The OPCW says the cost of destroying chemical materials alone will run between 25 and 30 million euros.

Syria has declared around 700 tons of most dangerous chemicals, 500 tons of less dangerous precursor chemicals and around 120 tons of isopropanol, which can be used to make sarin gas.

Hydrolysis systems aboard the US ship Cape Ray are to mix the chemicals with heated water and other chemicals to break down the lethal agents, resulting in a sludge equivalent to industrial toxic waste.

UN Security Council Resolution 2118 was passed after a massive chemical weapon attack that killed hundreds in several opposition areas around Damascus in August.

Rebels and the regime exchanged blame for that attack. - Sapa-AFP