Deadly exchanges between Israel and Hezbollah in Lebanon put a newly signed deal to end the Middle East war under further strain on Friday, after the postponement of planned US-Iran talks in Switzerland.

Experts says that any continuation of conflict in Lebanon is the biggest threat to deal.

Israel and the Lebanese government have entered their own U.S.-mediated direct negotiations, of which Hezbollah was not part. Those talks have yielded several announced ceasefires…