Talks to end the war between the United States and Iran hit a crisis after Iran said it would close the Strait of Hormuz, a key Middle East oil transit route, citing Israel's airstrikes in Lebanon. The clashes in Lebanon are also disrupting the two sides' meeting in Switzerland.
On the afternoon of the 21st (local time), U.S. and Iranian delegations sat down in Bürgenstock, Switzerland, as tensions rose over the Strait of Hormuz. The day before, Khatam al-Anbiya Central Headquarters under Iran's armed forces declared it would block passage through the strait. Tehran said Israel's military operation in Lebanon violated Article 1 of the U.S.-Iran memorandum of understanding (MOU) for ending the war. The provision says, "Immediately and permanently end military operations on all fronts, including Lebanon."
The Lebanon front has emerged as the biggest variable in the talks. The United States and Iran agreed to halt military operations on all fronts, but Israel and Hezbollah, the parties to the Lebanon front, are not signatories. Even after the two sides reached a dramatic cease-fire agreement on the 19th, sporadic attacks continued, heightening tensions. The Lebanon issue was also a key agenda item at the Switzerland talks that day.
The problem is that the Lebanon front is not a simple local conflict. The roots of the Lebanon crisis go back decades. Hezbollah, a Shiite armed faction backed by Iran, is one of the most powerful paramilitary organizations in the Middle East. Since expanding its influence in Lebanon in the 1980s, it has long clashed with Israel. Hezbollah denies Israel's very existence and, with Iran's support, has amassed large numbers of rockets, missiles and drones. The Lebanon front is effectively a proxy war between Iran and Israel.
Israel, for its part, has repeatedly carried out operations targeting Hezbollah. In 2006, after a Hezbollah cross-border raid and the abduction of two Israeli soldiers, it waged large-scale air and ground campaigns for more than a month. The war wound down with the adoption of U.N. Security Council Resolution 1701, but clashes between the two sides continued for nearly 20 years after. In Nov. 2024, Israel and Hezbollah agreed to a cease-fire that paused fighting for 60 days and withdrew forces from southern Lebanon, but the deal was effectively not implemented.
The Lebanon front ultimately exploded again this year amid the Israel-Iran war. In early March, Hezbollah barraged northern Israel with rockets in retaliation for attacks on Iran. According to Lebanon's Health Ministry, as the fighting escalated, Israeli airstrikes in Lebanon killed 4,057 people since March 2.
Iran has made halting attacks on Hezbollah, its most important ally in the Middle East, a core demand in the end-of-war talks. Tehran ultimately succeeded in including in Article 1 of the MOU that "the United States, Iran and the allies of the current war will immediately and permanently end military operations on all fronts, including Lebanon, and will not initiate any war or military operation against each other in the future."
But Israel, which is not a party to the MOU, is continuing military operations in Lebanon. Prime Minister Benjamin Netanyahu said after the MOU details were released, "We will restore security in northern Israel," adding, "To do that, we must maintain a security zone in southern Lebanon." It was a reaffirmation that Israel will not withdraw from Lebanon.
In the end, observers say how the Lebanon issue is resolved depends on the choice of U.S. President Donald Trump. Trump is pressuring Netanyahu to halt the Lebanon offensive on one hand, while urging Iran to rein in Hezbollah on the other. He warned on his Truth Social account that day, "Iran must immediately stop Hezbollah, its Lebanon proxy, from causing trouble," adding, "If not, we will strike Iran again very strongly, as we did last week."
Danny Citrinowicz, a former head of the Iran desk at Israel's Military Intelligence Directorate, told CNN, "The biggest obstacle to a broader agreement with Iran remains Lebanon," adding, "The key is how willing the United States is to strongly enforce a cease-fire that both sides interpret differently."