"Global jihad" is the term Israel uses for forces influenced by al-Qaida. Syria's rebels include al-Qaida-allied groups.
Syria has rarely acknowledged possessing chemical weapons.
Prime Minister Benjamin Netanyahu referred to threats from Syria and Iran at a Cabinet meeting Sunday. Iran is Syria's main regional ally.
"We must look around us, at what is happening in Iran and its proxies and at what is happening in other areas, with the deadly weapons in Syria, which is increasingly coming apart," he said.
Israel views Iran as an existential threat because of its nuclear and missile programs and support for violent anti-Israeli groups in Lebanon and Gaza, as well as repeated references by Iranian leaders to Israel's destruction. Iran denies it is seeking to build atomic weapons, insisting its nuclear program is for civilian purposes.
On Friday, Israeli Channel 2 TV broadcast an interview with a former Iranian diplomat who defected to the West in 2010. He warned that if Tehran gets nuclear weapons, it would use them against Israel. He did not provide evidence.
Part of Mohammad Reza Heydari's job was to draft foreign scientists to work on Tehran's nuclear program and he brought many from North Korea into Iran, the report said.
Heydari spoke from Oslo, where he has received political asylum.