"The Organisation for the Prohibition of Chemical Weapons has received an initial disclosure from the Syrian government of its chemical weapons programme," an OPCW statement said.
Its Technical Secretariat is now examining the details, it said.
A UN diplomat said the OPCW had received the Syrian declaration on Thursday. "It is quite lengthy," he said.
The organisation has postponed a meeting of its Executive Council set for Sunday that had been due to discuss how to dismantle Syria's chemical weapons programme.
Damascus had until Saturday to supply details of its arsenal, in line with a US-Russian plan that helped prevent military action on regime targets following a chemical attack last month that killed hundreds of people.
The plan stipulates that Assad's regime hand over its chemical weapons and facilities, which would be destroyed by mid-2014.
US Secretary of State John Kerry said he and his Russian counterpart Sergei Lavrov spoke on the telephone Friday about a "strong" UN Security Council resolution on ridding Syria of chemical weapons.
"We talked about the cooperation which we both agreed to continue to provide, moving not only towards the adoption of the OPCW rules and regulations, but also a resolution that is firm and strong within the United Nations," Kerry said.
"We will continue to work on that," said Kerry.
The Security Council's five permanent members -- the United States, China, Russia, France and Britain -- have been wrangling over the text of the resolution since Monday in a bid to find common ground.
Russia, a key ally of Damascus, opposes all references to a possible use of force
On the ground, jihadist rebels fought fiercely for the town of Azaz on the Turkish border before seizing it Wednesday from mainstream Free Syrian Army (FSA) rebels.
The move by Al-Qaeda front group the Islamic State of Iraq and the Levant (ISIS) triggered the ire of the National Coalition opposition group.
It issued a rare condemnation of ISIS, accusing the jihadists of violating the principles of the anti-Assad uprising.
The Syrian Observatory for Human Rights said that the Northern Storm brigade loyal to the FSA has agreed to a truce with ISIS.
Liwa al-Tawhid, another brigade loyal to the FSA, brokered the deal and sent fighters to deploy between the two sides in Azaz, the Observatory said.
Symbolic and strategic
Azaz has both symbolic and strategic value as it was one of the first towns to be captured from government troops, in July 2012, by the FSA which set up its own administration.
Tensions have spiralled between some mainstream rebel groups and ISIS in recent months, especially in northern Syria, where the opposition controls vast swathes of territory.
Deputy Prime Minister Qadri Jamil said the war is now in stalemate and Damascus would call for a ceasefire if long-delayed peace talks in Geneva take place.
"Neither the armed opposition nor the regime is capable of defeating the other side," Jamil told Britain's Guardian newspaper.
Asked what his government would propose at the stalled Geneva II summit, he replied: "An end to external intervention, a ceasefire and the launching of a peaceful political process."
In New York, UN envoys were set to resume talks on a draft Security Council resolution that would enshrine the US-Russian plan to neutralise Assad's chemical weapons.
According to Kerry, a UN report after inspections on the ground last month has proved the Syrian regime was behind the deadly chemical weapons attack in August in the suburbs of Damascus.
French President Francois Hollande, who has taken a strident stand against Damascus, is to meet his Iranian counterpart on the sidelines of the UN General Assembly next week, Hollande's office announced Friday.
The meeting on Tuesday between Hollande and Iranian President Hassan Rowhani would focus on the Syrian conflict as well as Iran's nuclear programme.
"What we want to see is an Iran fully engaged, like other players, in the search for a real political transition in Syria," an aide to Hollande said.
Rowhani, whose country is a close ally of the Assad regime, has offered to broker talks between the Syrian opposition and the Damascus regime.