Syria has started moving chemical weapon materials out of the country in a crucial phase of an internationally backed disarmament program that has been delayed by war and technical problems.

The Organization for the Prohibition of Chemical Weapons said on Tuesday that "priority chemical materials" were transported to the port of Latakia and onto a Danish vessel that was now sailing toward international waters.

China joined the escort mission as the frigate Yancheng entered Syrian waters on Tuesday along with ships from Russia, Denmark and Norway.

Foreign Ministry spokeswoman Hua Chunying said that transferring the chemical weapons in a fast and timely manner is conducive to the eventual elimination of chemical weapons in Syria.

China will continue to strengthen cooperation with the parties involved to ensure a safe and smooth transfer, she said.

Syria agreed to give up its chemical weapons by June under a deal proposed by Russia and agreed with the United States after a sarin gas attack on Aug 21 that Western nations blamed on President Bashar al-Assad's forces. Damascus blames rebels for the attack.

War, bad weather, bureaucratic and technical issues all contributed to missing a Dec 31 deadline for the removal of the most deadly toxins from Syria.

The OPCW did not disclose what percentage of Syria's 1,300-metric-ton toxic arsenal had been removed, but it said nine containers of the most dangerous chemical materials were on the Danish cargo vessel.

Escorted by the Chinese, Danish, Norwegian and Russian naval vessels, the ship will anchor offshore until more chemicals arrive at Latakia and then return to collect them.

Government forces have taken back control of the highway needed to transport the toxins to the coast.

Rebels were ousted from three towns along the road, but activists say convoys moving along it will remain vulnerable to rebel ambushes.

Washington welcomed the removal of the chemical materials and said Assad's government appeared to be sticking to the deal.

"Much more needs to be done," State Department spokeswoman Jen Psaki said at a news briefing, adding, "We have no reason to believe that the regime has gone back on any aspect of their promise."

Reuters-China Daily