One suspect, Ali Johari, allegedly passed on information to Mossad about construction projects under way by a building firm with ties to the Revolutionary Guards. A third suspect was sentenced on other espionage charges.

So far, neither party appears willing to drop out, despite tempting offers reportedly made to Zehut leader Moshe Feiglin, who scheduled a party conference in Tel Aviv for Tuesday.

As drone strikes become more frequent, the risk of unwanted escalation becomes greater.

More than 50 members of rebel and government forces killed in recent fighting in Hama and Idlib provinces.