The deal came amid growing momentum towards peace talks after more than two-and-a-half years of Syria's deadly uprising, with the rebels suffering a string of recent setbacks.
Five rebel commanders have been killed since Thursday, including two chiefs of rebel battalions who died fighting loyalist forces near the international airport outside second city Aleppo.
The army has been pressing a campaign to retake rebel-held areas in Aleppo and jihadist fighters have called for mass mobilisation to counter regime advances.
A Syrian media report said that a long-delayed peace conference could be held in Geneva on December 12.
The international community has been trying for months to convene a peace conference dubbed "Geneva II". But proposed dates have come and gone with no progress.
The regime has said it is willing to attend, provided Assad's departure is not on the table. The opposition, though, insists on Assad's departure and exclusion from the transition process.
The talks at OPCW headquarters in The Hague broke off twice before agreement was reached around 2000 GMT, as delegates thrashed out the final draft.
Under the deal, Syria's weapons will be taken out of the war-ravaged country, where an estimated 120,000 people have been killed during the uprising, to ensure their destruction in the "safest and soonest manner", the OPCW said in a statement.
Almost all of Syria's chemicals and precursors, except for isopropanol which can be used to make sarin nerve gas, must be removed from the country by February 5, 2014.
'Most critical' chemicals out of Syria by New Year
The "most critical" chemicals must be removed by the end of the year, the OPCW said.
Declared chemical weapons facilities will be destroyed between December 15 and March 15, 2014, "according to a risk-based criterion", the watchdog said.
Likewise, "priority" chemicals will be destroyed outside of Syria by April 2014, and all other chemicals by the already agreed deadline of June 30, 2014.
Sigrid Kaag, who is coordinating the joint UN-OPCW mission in Syria, told the meeting: "I am currently reaching out to others to consider joining this international effort".
Despite a US request of its staunch ally, Albanian Prime Minister Edi Rama said earlier that he would not help destroy Syria's arsenal in his country after a string of domestic protests against the move.
"It is impossible for Albania to take part in such an operation... as it has no capacity" to carry out such a task, Rama told reporters.
His statement was broadcast live on giant television screens on Tirana's main square, where thousands of demonstrators erupted in cries of joy.
Malik Ellahi, political adviser to OPCW head Ahmet Uzumcu, said that he could not yet say where Syria's chemicals would be taken for destruction.
"But the Executive Council has adopted a decision and has confidence that there are alternatives and that this material will be shipped out of Syria," he told journalists.
"The target dates have been set with the confidence that there will be alternatives for destruction," he said.
The focus of Syria's chemical disarmament is increasingly on how the world can help, and it was not immediately clear which country could receive and destroy the lethal chemicals and precursors after Tirana's refusal.
Norway has also said no, citing time constraints and inexperience, while France and Belgium are also believed to have been asked for possible help by Washington.
Norway and Denmark have said they would provide ships to help take the chemicals out of Syria, with Denmark saying it would also provide a personal protection team for international inspectors.
A team of UN-OPCW inspectors has been on the ground since October checking Syria's weapons and facilities, but security remains a concern.
OPCW head Uzumcu wrote to Kaag on November 11 laying out a tentative plan for the destruction, a diplomatic source told AFP, with all chemicals leaving Syria via Latakia, Syria's main port on the Mediterranean.
Uzumcu said that the Syrians had requested equipment to help the process, including armoured 4x4 vehicles and electronic counter measure (ECM) equipment.
Western nations refuse to supply them as they could be used against rebels. Syria's ally Russia could, however, supply such dual-purpose equipment.
The joint Russian-US Syrian chemical weapons disarmament plan was endorsed by the UN Security Council in September to head off military strikes in retaliation for the regime's alleged use of the weapons against its own people after a chemical attack against a Damascus suburb in August left hundreds dead.