Washington confirmed the Israeli assessment, thus posing a problem for US President Barack Obama, who had said use of chemical arms would be a “red line.”
Israel’s deputy foreign minister urged US action in Syria — a call slapped down by more senior figures.
Israeli Ambassador to the US Michael Oren said it was not making any policy recommendations to Obama on Syria.
“We think this issue is very complex,” he said.
Several officials said Israel would be unlikely to attack Syria unilaterally unless it had evidence that chemical weapons had been handed over to Hezbollah.
Lacking enough of the specialized ground troops that would be needed for a search-and-destroy sweep of chemical weapons, Israel would probably have to rely on aerial bombing.
The Netanyhau government might even acquiesce if the rebels acquire the chemical weapons, on the assumption that the insurgents were mainstream Syrians keen to rebuild their country and loath to invite catastrophic war with Israel.
“If the jihadis get the chemical weapons, that’s very bad, but there’s still the hope that these people lack the hard-core military wherewithal, and required technical support in Syria, that would be required to use them,” one Israeli official said.
Indeed, Israeli planners are debating to what extent the radical Sunni Islamists fighting al-Assad could eventually constitute a direct threat to Israel.
Israel’s chief military spokesman, Brigadier-General Yoav Mordechai, sounded the alarm last month by saying the “global jihad” — meaning al-Qaeda and its affiliates — wielded the most clout on the Syrian-held side of the Golan Heights.
Other Israeli authorities are more optimistic. The Mossad intelligence agency estimates that Syria’s entrenched secularism will dilute enmity to Israel, one official said.
“The Islamists there aren’t all Salafists, and the Salafists aren’t all al-Qaeda, by any means,” the official said. “We may not make peace, but I think we might find some kind of dialogue, if only for the sake of mutual deterrence.”
Israel has given no indication that it already has contacts with Syria’s opposition, but it has coordinated closely on security with Jordan, a supporter of some rebel factions.
Back in Yaakov’s courtroom, the fate of Massarwa, who faces a maximum of 15 years in jail if convicted, rests on whether the state can prove there is danger to Israel from the Free Syrian Army unit he stayed with for a week in March.
Massarwa’s lawyer, Helal Jaber, hopes the logic of “my enemy’s enemy is my friend” will win clemency for his client, who went to Syria via Turkey in search of a missing brother who had separately joined the rebels.
“The greatest democracies in the world, including the United States, are supporting the opposition to al-Assad,” Jaber said. “So how can Israel fault someone for doing the same?”
Additional reporting by Warren Strobel and Crispian Balmer