TEHRAN, Iran 

Iranian President Masoud Pezeshkian on Tuesday threatened a “severe and regret-inducing” response to any “aggression” against his country, following a threat by US President Donald Trump to attack Iran again

"The response of the Islamic Republic of Iran to any unjust aggression will be severe and regret-inducing," Pezeshkian said on the US social media company X.

On Monday, Trump said he would support an Israeli attack on Iran if Tehran resumes its nuclear program, warning that he would "knock the hell out of them."

Flanked by Israeli Prime Minister Benjamin Netanyahu at his Palm Beach estate in Florida, Trump also claimed that Iran is trying to expand its ballistic missile program.

“Now I hear that Iran is trying to build up again. And if they are, we’re going to have to knock them down,” Trump said, adding that he heard Tehran wants to negotiate a deal with Washington.

During a 12-day war in June, the US targeted three major Iranian nuclear facilities, including Fordo, Natanz, and Isfahan, using bunker-buster bombs.

Following the strikes, which Iran strongly condemned, Trump claimed that the Iranian nuclear program had been "obliterated," a statement he has repeated multiple times since, with Iranian officials neither confirming nor denying it.

While a US-mediated ceasefire between Tehran and Tel Aviv has held since June, tensions have continued to simmer.

According to some reports, a possible new round of strikes on Iran’s missile and ballistic missile programs was among the key topics discussed during Netanyahu’s latest meeting with Trump — his fifth this year.

Ali Shamkhani, a senior adviser to Iran's Supreme Leader Ayatollah Ali Khamenei, was the first to respond to Trump’s remarks on Monday, saying that "any act of aggression will face a harsh and immediate response."

Shamkhani said that Iran’s missile and defensive capabilities "are neither containable nor in need of anyone’s permission."

The former top security official, who survived an Israeli attack during the 12-day war, warned that any attacks against Iran "will be met with a harsh, immediate response beyond the imagination of its architects."