The US special envoy for Syria Tom Barrack on Thursday warned Hezbollah against getting involved in the war between its main backer Iran and Israel.

"I can say on behalf of President (Donald) Trump... that would be a very, very, very bad decision," Barrack said, responding to a question on what the US position would be on any involvement by Hezbollah in the war.

Barrack met with Lebanese President Joseph Aoun at Baabda Palace and Speaker Nabih Berri in Ain el-Tineh.

Hezbollah has condemned Israel's strikes on Iran and expressed full solidarity with its leadership.

Hezbollah on Thursday expressed support for Iran’s Supreme Leader Ali Khamenei following threats by Israeli leaders that he could be killed.

In a statement, Hezbollah said that “threats to assassinate (Khamenei) are foolish and reckless, and will have disastrous consequences.”

But the group has stopped short of making explicit threats to intervene.

Israel's defense minister said Thursday that Khamenei "can no longer be allowed to exist" after an Israeli hospital was hit during an Iranian missile attack.

"Khamenei openly declares that he wants Israel destroyed -- he personally gives the order to fire on hospitals. He considers the destruction of the state of Israel to be a goal," Israel Katz told journalists in Holon near Tel Aviv. "Such a man can no longer be allowed to exist."

Killing Khamenei would "end the conflict" between Israel and Iran, Israeli Prime Minister Benjamin Netanyahu has said.