BEIRUT >> An advance group of international inspectors arrived in Syria today to begin the ambitious task of overseeing the destruction of President Bashar Assad’s chemical weapons program, kicking off a mission that must navigate the country’s bloody civil war as well as the international spotlight.

Twenty inspectors from a Netherlands-based chemical weapons watchdog crossed into Syria from neighboring Lebanon on their way to Damascus to begin their complex mission of finding, dismantling and ultimately destroying an estimated 1,000-ton chemical arsenal.

The experts have about nine months to complete the task, which has been endorsed by a U.N. Security Council resolution that calls for Syria’s chemical stockpile to be eliminated by mid-2014. It is the shortest deadline that experts from the Organization for the Prohibition of Chemical Weapons have ever faced in any nation, and their first mission in a country at war.

Upon arrival in Damascus, the inspectors are expected to meet with Foreign Ministry officials later today.

Experts at The Hague, where the OPCW is based, said Sunday the inspectors’ priority is to achieve the first milestone of helping Syria scrap its ability to manufacture chemical weapons by a Nov. 1 deadline, using every means possible. That may include smashing mixing equipment with sledgehammers, blowing up delivery missiles, driving tanks over empty shells or filling them with concrete, and running machines without lubricant so they seize up and become inoperable.

Some of the inspectors will be double-checking Syria’s initial disclosure of what weapons and chemical precursors it has and where they are located. Others will begin planning the logistics for visits to every location where chemicals or weapons are stored.

Within a week, a second group of inspectors is scheduled to arrive — fewer than 100 combined — and form teams that will fan out to individual sites. Their routes are secret — both for their safety and because Syria has the right not to reveal its military secrets, including base locations.

The inspectors’ mission was born out of a deadly chemical attack on opposition-held suburbs of Damascus on Aug. 21. The U.S. and its allies accuse the Syrian regime of being responsible, while Damascus blames the rebels.

The chemical attack prompted the Obama administration to threaten punitive missile strikes against the Assad regime, touching off weeks of frantic diplomacy that ended with the U.N. resolution Friday to purge Syria of its chemical weapons program.

The resolution also endorsed a roadmap for political “transition” in Syria adopted by key nations in June 2012, and it called for an international peace conference in Geneva to be convened “as soon as possible” to implement it.

The negotiations planned for Geneva have been repeatedly delayed for months, with neither the Syrian regime nor the opposition showing much interest in attending while the war on the ground remains stalemated. Disagreements also have flared repeatedly over who should take part in the talks that aim to broker a political solution to the conflict.

Efforts to bring the sides to the table received another blow over the weekend when Syria’s foreign minister said the government won’t talk with the main Western-backed opposition group, the Syrian National Coalition. The coalition, meanwhile, faces internal splits over whether to attend a Geneva conference.

Russia, a close ally of Syria, tried to smooth things over today, with Foreign Minister Sergey Lavrov saying that “reasonable” Syrian rebels could take part in prospective peace talks. Speaking to reporters in Moscow, Lavrov said Western powers should help encourage rebels who don’t harbor “extremist or terrorist views” to take part.

The rebel movement on the ground also is riven by fissures, both ideological and political. Those differences have burst to the fore in recent months as Islamic extremist rebel brigades associated with al-Qaida have battled more mainstream rebel factions nominally linked to the Western-backed Free Syrian Army.

In an audio message posted on a militant website on Monday, a spokesman for one of the most powerful Islamic extremist rebel groups, the Islamist State in Iraq and the Levant, accused more moderate rebels of “stealing” credit for battlefield victories from his group.

Abu Mohammed al-Adnani said commanders of the Free Syrian Army are claiming territorial gains made by al-Qaida fighters. He points to the capture of the Mannagh air base in northern Syria as an example, saying some FSA fighters took part in the battle for the base and an FSA commander took credit for it, but it was actually captured by al-Qaida.

Al-Qaida militants have in the past year emerged as some of the most organized and successful fighting forces on the opposition side in Syria.

Associated Press writer Laura Mills in Moscow contributed to this report.