LONDON -- The U.K. will help the international mission to destroy Syria's chemical weapons program, officials said Friday, joining a complex operation with prominent roles for the U.S., Denmark and Norway.

Britain's Foreign Office said it has agreed to destroy 150 tons of two industrial-grade chemicals from Syria's stockpile at a commercial facility. The chemicals used in the pharmaceutical industry will be shipped to the U.K. before being transferred to a commercial site to be incinerated and destroyed, it said in a statement.

"It is important to stress that these are chemicals, not chemical weapons," the Foreign Office said, explaining that the two chemicals only become highly toxic when mixed to make a nerve agent.

The commitment adds another layer to the complex and unprecedented operation to destroy Syria's chemical weapons stockpile, which comes after the confirmed use of chemical weapons in the Damascus suburb of Ghouta on Aug. 21 , which the U.S. government says killed 1,400 people. A number of questions remain about how Syria's chemical weapons arsenal will be destroyed, including what will be done with the material once it is rendered harmless.

The Foreign Office said the two chemicals would be removed from Syria separately, sealed in standard industrial containers to international standards and under the supervision of chemical weapons watchdogs.

Under the plan by the Organization for the Prohibition of Chemical Weapons, chemicals will be transported from 12 storage sites to Latakia in Syria. Russia is providing armoured trucks and other equipment to help transport them.

The chemicals will then be loaded onto Danish and Norwegian ships and shipped to an Italian port, where the most toxic chemicals -- including materials used to make mustard gas and sarin -- will be transferred to a U.S. ship for destruction at sea.

That ship -- MV Cape Ray -- is serving as the linchpin of the plan. The Cape Ray will have machinery that will neutralize the chemicals by mixing them with other chemicals and heated water.

Under the current plan, the most toxic chemicals are to be removed from the country by Dec. 31. All other chemicals declared by Syria are to be removed from the country by Feb. 5, with the exception of around 100 tons of isopropanol, which are to be destroyed in Syria by March 1. All chemicals are to be destroyed by June 30.

However, Ahmet Uzumcu, director-general of the Organization for the Prohibition of Chemical Weapons, has warned there may be delays.