TEHRAN, April 9 -- The fragile two-week truce between Iran and the United States was hanging in the balance on Wednesday, with Tehran threatening to resume hostilities as Israel launched a major bombardment of Lebanon.

Washington and Tehran both claimed victory after agreeing to a two-week ceasefire and negotiations aimed at ending a war that has killed thousands across the Middle East and sparked global economic upheaval.

But the deal's fractures emerged quickly as Israel carried out its heaviest strikes on its neighbour - including in densely packed central Beirut - since the Iran-backed group Hezbollah joined the war in early March.

At least 182 people were killed and nearly 900 wounded on Wednesday, the Lebanese Health Ministry sai...