People gather at the site of an Israeli airstrike that targeted a building in Beirut's southern suburbs on Sunday.

Iran’s top security official warned Sunday that Lebanon is central to Tehran’s regional security posture, saying any breach of the Islamic Republic’s “red lines” would not be tolerated.

Mohammad Bagher Zolghadr, secretary of Iran’s Supreme National Security Council, wrote on X that “the unity of the fronts has created a security chain in defense of the region.”

“Lebanon is our lifeblood, and any violation of the Islamic Republic’s red lines will not be tolerated,” he added.

Iranian Parliament Speaker Mohammad Bagher Ghalibaf also said in a post on X on Sunday that Israel “will never be able to isolate and corner any part of the Resistance’s pillars,” in an apparent reference to the Lebanese militant group Hezbollah.

“The powerful diplomacy of Iran will guarantee the sovereignty and territorial integrity of beloved Lebanon, and will put an end to the Israeli regime’s madness and warmongering,” Ghalibaf, Iran’s chief negotiator in the talks, added.

“Carry on, and we will too,” Ghalibaf wrote.

The Iranian officials comments came after US President Donald Trump earlier Sunday urged Israel not to strike Lebanon as Washington and Tehran negotiate a memorandum of understanding related to the war.

“This morning’s attack on Beirut should not have happened,” Trump wrote on Truth Social. “Particularly on a special day when we are so close to a Peace Deal with Iran.”

Trump also told CNN political and global affairs analyst and Axios reporter Barak Ravid that the signing of the memorandum with Iran remains on track for later Sunday despite Israel’s latest strike on Beirut. In those comments, Trump sharply rebuked Israeli Prime Minister Benjamin Netanyahu.