The Syrian regime has not fully complied with the agreement it signed two years ago to join the international Chemical Weapons Convention and dismantle its entire chemical weapons programme.
The Russian-brokered deal was signed in 2013 after the US threatened to attack the Assad regime in retaliation for its alleged use of chemical weapons against civilians.
Around 1,400 residents of a Damascus suburb were believed to have been killed by short-range missiles containing sarin gas.
According to an extensive report in the Wall Street Journal based on interviews with US administration officials and international inspectors, around 1,300 metric tons of chemicals that were destined to be used to prepare sarin and VX nerve agents were destroyed.
However, the report added that the Organisation for the Prohibition of Chemical Weapons inspectors were not given access to a number of research facilities still active in Syria and that the regime had succeeded in hiding some of the chemicals it had promised to hand over.
Although the inspectors suspected that they had not been shown everything, they decided not to press the Syrians too closely on the issue because they did not want to jeopardise the cooperation they had already achieved. In addition, they were reliant on the Syrian army for security.
The Israeli intelligence assessment has been that while nearly all the chemical weapon stockpiles were destroyed or removed, the Syrian military can still manufacture a small quantity of the banned substances.
Israeli analysts added that the regime now mainly uses chlorine - not considered a chemical weapon by international treaties - when it launches chemical attacks on rebels and civilians.
Owing to the time required to manufacture more of the most dangerous chemicals and the ongoing retrenchment of the Syrian army, it is thought unlikely that such weapons will be used against Israeli targets in the foreseeable future.