TEHRAN, Iran (AFP) — The fragile two-week truce between Iran and the United States (US) 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 militant group Hezbollah joined the war in early March.

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

Israel said its battle against Hezbollah was not part of the US-Iran truce agreed late Tuesday, an argument echoed by US Vice President JD Vance, days before he is due to lead talks with Tehran in Pakistan.

“If Iran wants to let this negotiation fall apart… over Lebanon, which has nothing to do with them, and which the United States never once said was part of the ceasefire, that’s ultimately their choice,” he said.

But Iran’s parliament speaker Mohammad Bagher Ghalibaf appeared to threaten the ceasefire, posting on X that the “workable basis on which to negotiate” had already been violated, making further talks “unreasonable”.

Adding to the fragility of the truce – agreed hours before a deadline set by US President Donald Trump – a senior US official said Iran’s 10-point plan was not the same set of conditions the White House had agreed to in order to pause the war.

More than 1,700 people have been killed in Lebanon since Israel launched airstrikes and a ground invasion last month, local officials said.

Iran’s Revolutionary Guards warned they would “fulfil our duty and deliver a response” if Israel did not cease its strikes there, while Hezbollah said it had a “right” to respond.

Pentagon chief Pete Hegseth also vowed that American forces remained at the ready if the conflict flared up again.

The belligerent rhetoric came ahead of high-stakes talks in Pakistan expected on Friday, after Iran temporarily agreed to reopen the Strait of Hormuz under threat of annihilation by Trump, with ships passing through the strategic waterway on Wednesday.

But reports suggested the waterway was shut again later in the day despite the ceasefire, prompting the White House to call on Iran to reopen it “immediately, quickly and safely”.

Further casting doubt on the truce’s durability, Iranian state media announced fresh “missile and drone attacks” on Wednesday against US-allied Gulf states in retaliation for airstrikes on its oil facilities.