The U.S.-Iran ceasefire does not apply to Israel's strikes against Hezbollah in Lebanon, White House press secretary Karoline Leavitt told Axios, contradicting claims from Iran and the Pakistani mediators.Why it matters: Israel's renewed attacks in Lebanon posed an immediate challenge to the stability of the ceasefire.Stopping the Israeli strikes against Hezbollah, its proxy in Lebanon, was one of Iran's key demands for the ceasefire. The Iranians are now threatening to resume the fighting and close the Strait of Hormuz if the fighting in Lebanon continues. State of play: Hezbollah launched missile strikes at Israel soon after the U.S. and Israel attacked Iran five weeks ago, opening a new front in the war.Israel responded with airstrikes in Beirut and other parts of the country, and later with a ground invasion and occupation of large swaths of southern Lebanon. Thousands of Israeli soldiers are in positions as deep as six miles into Lebanese territory. The Israeli government says it will not pull out its troops and will not allow hundreds of thousands of displaced Lebanese civilians to return home until Hezbollah is disarmed.Driving the news: On Tuesday, when Pakistani Prime Minister Shehbaz Sharif announced the ceasefire, he said it would apply "everywhere, including Lebanon and elsewhere."Shortly afterward, Israeli Prime Minister Benjamin Netanyahu issued a statement claiming the ceasefire did not include Lebanon. The U.S. did not make its own position clear prior to Leavitt's statement to Axios.It's not clear whether the U.S. agreed at any point in the negotiations that the ceasefire would apply to Lebanon.Behind the scenes: A senior U.S. official said Netanyahu raised the issue of Lebanon in a phone call with President Trump shortly before the announcement of the ceasefire. Trump and Netanyahu agreed during the call that the fighting in Lebanon could continue, the U.S. official and an Israeli official said.The U.S. official said the White House is not currently concerned that the situation in Lebanon would cause the ceasefire with Iran to collapse.On Wednesday, the Israel Defense Forces conducted a massive wave of strikes against Hezbollah targets in Beirut, in the Beqaa Valley and in southern Lebanon.The IDF said it was "the largest coordinated wave of strikes in Lebanon" since the start of the war in Iran. 50 Israeli Air Force fighter jets participated in the strikes and attacked 100 Hezbollah command centers and military infrastructure sites using approximately 160 munitions, the IDF said. According the the Lebanese Red Cross, more than 80 people have been killed and 200 wounded.The other side: Iran's Tasnim news agency quoted sources who said Iran would withdraw from the ceasefire agreement if the attacks on Lebanon continue. Fars news agency said oil tankers passing through the Strait of Hormuz had been stopped on Wednesday after the massive Israeli strikes. What they're saying: Lebanese Prime Minister Nawaf Salam also accused Israel of breaching the ceasefire. The Lebanese presidency called the Israeli strikes "a new massacre." Iran's foreign minister, Abbas Araghchi, said in calls with several foreign ministers that the Israeli strikes in Lebanon were a breach of the ceasefire.Sharif wrote on X that ceasefire violations had "been reported at few places across the conflict zone which undermine the spirit of peace process. I earnestly and sincerely urge all parties to exercise restraint and respect the ceasefire for two weeks, as agreed upon, so that diplomacy can take a lead role towards peaceful settlement of the conflict."Hezbollah said it had a right to respond to Israeli's attack.