Lebanon Clashes Put US-Iran Ceasefire at Risk

Renewed fighting between Israel and Hezbollah in southern Lebanon is threatening the fragile ceasefire agreement between the United States and Iran. The violence has delayed broader negotiations on Iran's nuclear programme and sanctions relief, and briefly prompted Iran to shut the Strait of Hormuz.

Hezbollah, an Iran-backed armed group, has been fighting Israel for decades. With Iranian support, it built a large arsenal of rockets, missiles, and drones. A major war in 2006 was followed by renewed clashes from late 2023, when Hezbollah began firing across the border in support of Hamas during the Gaza war. Israel killed Hezbollah's leader Hassan Nasrallah in 2024. A ceasefire in late 2024 aimed to withdraw Israeli forces from southern Lebanon, but troops remained and strikes continued.

Violence escalated after Israel and the US killed Iran's supreme leader in an airstrike in late February. Hezbollah responded with fire on northern Israel, and Israeli forces pushed deeper into Lebanon, displacing residents and destroying homes. Lebanon's health ministry reports over 4,000 deaths since early March.

The 14-point US-Iran agreement opens with a call to end fighting "on all fronts, including in Lebanon," and commits both sides to respecting Lebanon's sovereignty. US President Donald Trump has said the deal requires a complete ceasefire covering Lebanon, Hezbollah, and Israel. For Iran, protecting Hezbollah is a central demand; Tehran wants guarantees that the Lebanon fighting will stop before resuming wider talks.

Israel has refused to withdraw. Prime Minister Benjamin Netanyahu said troops will stay in a buffer zone in southern Lebanon as long as needed. National Security Minister Itamar Ben Gvir said Israel would not sacrifice citizens' safety. Hezbollah denies violating the ceasefire and accuses Israel of continuing the war.

Trust between Tehran and Washington remains thin. A senior Iranian lawmaker said the US failure to honour the Lebanon clause shows Washington has not earned Iranian trust. Trump and Vice President JD Vance have expressed frustration with Israel's continued strikes, but Trump has avoided a public break with Netanyahu, calling the US-Israel relationship "great."

Analysts say Lebanon, not the nuclear file, may now be the biggest obstacle to a lasting deal. A former Israeli military intelligence official described Lebanon as the chief risk to any broader understanding with Iran, noting that Washington and Tehran read the ceasefire terms differently.