A specially equipped United States ship has finished neutralizing all 600 metric tons of the most dangerous of Syria's chemical weapons components surrendered to the international community this year to avert threatened airstrikes, the Pentagon said on Monday.

It said the Cape Ray, equipped with the US-developed Field Deployable Hydrolysis System, neutralized 581.5 tons of DF, a sarin precursor chemical, and 19.8 tons of HD, an ingredient of sulfur mustard, while afloat in the Mediterranean.

The vessel will travel to Finland and Germany in the next two weeks to unload the resulting effluent, which will undergo treatment as industrial waste to render it safer, a Pentagon spokeswoman said.

It was the first time that chemical weapons components had been neutralized at sea, the Pentagon said.

Damascus agreed in September to a Russian proposal to give up its chemical weapons to avert threatened military strikes by the US and France, which accused Syria of using the arms against opponents of President Bashar al-Assad.

A number of countries are involved in eliminating the chemical stockpiles. The US was selected to dispose of the worst of the chemical weapons components because it had recently developed a mobile version of the hydrolysis system it uses for neutralizing chemical stockpiles.

The system uses substances and mixtures such as water, sodium hydroxide and sodium hypochlorite to neutralize bulk amounts of chemical warfare agents, according to the US Army's Edgewood Chemical Biological Center.

Earlier this year, the hydrolysis system was placed aboard the Cape Ray, a 198-meter vessel that is part of the US Maritime Administration's ready reserve force of 46 ships.

US President Barack Obama hailed the completion of the destruction of Syria's chemical weapon stockpile, but said Washington would seek to ensure that Damascus fulfills all its commitments.

"Today we mark an important achievement in our ongoing effort to counter the spread of weapons of mass destruction by eliminating Syria's declared chemical weapons stockpile," Obama said in a statement.

He said the destruction sent "a clear message that the use of these abhorrent weapons has consequences and will not be tolerated by the international community.

"Going forward, we will watch closely to see that Syria fulfills its commitment to destroy its remaining declared chemical weapons production facilities," Obama said.

US Secretary of State John Kerry reiterated that "much more work must be done" as he marked what he said was "a milestone in our unrelenting work to ensure the end of the Assad regime's deadly chemical arsenal."

Reuters - AFP