BEIRUT - International disarmament experts on Sunday began dismantling and destroying Syria’s chemical-weapons arsenal and the equipment used to produce it, taking the first concrete step in their colossal task of eliminating the country’s chemical stockpile by mid-2014, an official said.

The inspectors from the Organization for the Prohibition of Chemical Weapons have about nine months to purge President Bashar Assad’s regime of its chemical program. The mission, endorsed by the United Nations Security Council, faces the tightest deadline in the watchdog group’s history and must simultaneously navigate Syria’s bloody civil war.

Sunday marked the fifth day that an advance team of about 20 inspectors has been in the country and the first day that involved actually disabling and destroying weapons and machinery, an official on the joint mission said.

The production equipment included filling and mixing machinery, some of it mobile, said the official, who spoke on condition of anonymity because of the sensitivity of the matter.

Equipment for producing chemical agents is to be destroyed by Nov. 1. International inspectors believe that Syria has 25 production facilities, eight of which are mobile, which are clustered near Damascus and in central Syria.

The Syrians are responsible for the physical demolition of the materials, while organization inspectors monitor the process and verify what is being destroyed, the official said. He declined to provide details or say where the work took place.

“The fact that just three weeks ago the Syrian regime did not even acknowledge it had chemical weapons, and now inspectors are not only on the ground but they are reportedly overseeing the initial stages of destruction is a positive step,” U.S. State Department spokesman Jen Psaki said in an emailed statement. “There is more work to be done and the world will be watching.”

This is just the beginning of a complicated process to eliminate Syria’s estimated1,000-ton chemical-weapons stockpile and the facilities that created it. Damascus developed its chemical program in the 1980s and 1990s, building an arsenal that is believed to contain mustard gas and the nerve agents sarin, VX and tabun.

The advance team arrived last week to lay the foundations for a broader operation of nearly 100 inspectors. Those already in Syria have been double-checking the Assad regime’s initial disclosure of what weapons and chemical precursors it has and where they are located.

U.S. officials say that while the Syrian government’s preliminary inventory of its chemical-weapons program was more extensive than some experts anticipated, it was not complete. A more formal - and, U.S. officials hope, more comprehensive - declaration is to be submitted by Syria to the Organization for the Prohibition of Chemical Weapons later this month.

Members of the team are planning visits to every location where chemicals or weapons are stored - from trucks loaded with munitions up to full production sites.

Inspectors can use any means to destroy equipment, including crude techniques like taking sledgehammers to control panels or driving tanks over empty vats. But the second phase - destroying battle-ready weapons - is more difficult, time-consuming and expensive.

According to senior U.S. officials, a major centerpiece of the disarmament effort will be a mobile and highly sophisticated system developed by the Pentagon that would probably be set up near Syria to neutralize large quantities of precursor chemicals that would be transported out of the country.

The system, known as the Field Deployable Hydrolysis System, is designed to convert chemical agents into compounds that cannot be used for military purposes by mixing them with water and other chemicals and then heating them. The system would be used to neutralize the large quantities of precursor chemicals that could be used by the Syrian government to make poison gas and thus replenish its chemical-weapons arsenal.

Such precursor chemicals make up the bulk of the Syrian arsenal, U.S. officials say.

A senior State Department official said that the use of the mobile system would provide an “early demonstration” that steps were being taken to shrink Assad’s chemical program and would make it easier to meet the mid-2014 target for its elimination.

“It will reduce the possibility that the Syrian regime can change its mind,” added the State Department official, who asked not to be identified because the plan for eliminating Syria’s poison gas program was still being finalized. “And finally, very importantly, it will greatly reduce the size and duration of the international footprint in Syria.”

The basic strategy behind the international disarmament plan is to destroy completed chemical bombs and warheads where they are or at nearby locations in Syria.

This would limit the need to transport them, which could expose them to theft by some of the many groups fighting in Syria. Small warheads can be destroyed in special devices. Large weapons may need to be drained of their chemical agents before they are destroyed.

All of this must be done amidst a bloody civil war that has laid waste to the country’s cities, shattered its economy, killed around 100,000 people and driven more than 2 million people to seek shelter abroad. Another nearly 5 million people have been displaced within the country, which has become a patchwork of rebel-held and regime-held territory.

The fighting pits the mainly Muslim Sunni opposition against the backers of Assad, whose Alawite faith is an offshoot of Shiite Islam.

Underscoring the physical perils the inspectors face, four mortar shells landed Sunday in the Christian quarter of al-Qasaa, killing at least eight people, according to Syria’s state news agency. It was unclear whether any organization experts were close to the explosions.

The disarmament mission stems from a deadly Aug. 21 attack on opposition-held suburbs of Damascus in which the U.N. has determined the nerve agent sarin was used. Hundreds of people were killed, including many children. The U.S. and Western allies accuse the Syrian government of being responsible, while Damascus blames the rebels.

President Barack Obama’s administration threatened to launch punitive missile strikes against Syria, prompting frantic diplomatic efforts to forestall an attack. Those efforts concluded with September’s unanimous U.N. Security Council resolution endorsing the elimination of Syria’s chemical weapons.

In an interview in a staterun newspaper Sunday, Assad said the Syrian regime began producing chemical weapons in the 1980s to “fill the technical gap in the traditional weapons between Syria and Israel.” He said production of chemical weapons was halted in the late 1990s but provided no further information.

Assad on Saturday told German magazine Der Spiegel that Germany could be an intermediary on behalf of Europe in Syria.

“I would be pleased if representatives from Germany would come to Damascus to talk about how things really are,” Assad said, adding that a negotiated solution with “militants” wouldn’t be possible.

Germany rejected Assad’s offer, Foreign Minister Guido Westerwelle told Spiegel Online in an interview in Kunduz in Afghanistan.

Assad told Der Spiegel that Syria may hold elections before his term ends in August and that he hasn’t yet decided whether he will be a candidate.

Information for this article was contributed by Associated Press writers Ryan Lucas, Diaa Hadid and Albert Aji of The Associated Press; by Donna Abu-Nasr and Indira A.R. Lakshmanan of Bloomberg News; and by Michael R. Gordon and Anne Barnard of The New York Times.

Front Section, Pages 1 on 10/07/2013