Syria has started moving chemical weapons 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 joint mission overseeing the disarmament, the UN and the Organization for the Prohibition of Chemical Weapons (OPCW), said on Tuesday that the materials had been moved from two sites to the port of Latakia and then loaded onto a Danish commercial vessel.

In separate interview with Al Jazeera, Sigrid Kaag, joint mission coordinator for the UN and OPCW, said the first shipment indicates the progress is being made.

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

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

China, Denmark, Norway and Russia are providing maritime security for the cargo.

The removal was due to take place before December 31, but Syria's worsening conflict, logistical problems and bad weather had delayed the operation.

The year-end deadline for the removal of weapons components was the first major milestone under a UN Security Council-backed deal arranged by Russia and the US that aims to eliminate all of Syria's chemical arms by the middle of this year.

Under the plan, the chemicals will be taken from the Syrian port of Latakia to a port in Italy, where they will be transferred to a US navy vessel, the Cape Ray, which is fitted with equipment to destroy them at sea.

The OPCW turned to the US military for assistance after no country volunteered to destroy the chemical weapons on its soil, despite an international consensus that the weapons be neutralized outside Syria.

The US-Russia deal was aimed at heading off US military strikes against President Bashar al-Assad's regime after hundreds of people were killed last August in a chemical weapons attack outside Damascus.

PHOTO CAPTION

Danish support vessel L17 "Esbern Snare" of the Danish-Norwegian task group which will transport Syria's chemical agents for destruction performs training in the Mediterranean Sea, in this handout photo released to Reuters on January 5, 2014 by the Norwegian Armed Forces.

Al-Jazeera