Iran’s Supreme Leader Ali Khamenei has vowed swift retaliation following US President Donald Trump latest threat.

“If any mischief is done by them [US and Israel], they will certainly receive a firm reciprocal blow. If the enemies think they can instigate sedition within the country, the Iranian nation itself will respond to them.” Khamenei warned during a televised address on Monday to mar the end of Ramadan.

Khamenei’s combative rhetoric comes in direct response to Trump’s inflammatory comments on Sunday where he warned of “unprecedented bombing” if Tehran doesn’t abandon its nuclear program.

“If they don’t make a deal, there will be bombing — and it will be bombing the likes of which they have never seen before,” Trump told NBC News’ Kristen Welker. “There’s a chance that if they don’t make a deal, that I will do secondary tariffs on them like I did four years ago.”

Earlier in the day, Iranian President Masoud Pezeshkian rejected direct negotiations with the United States, but indicated a possibility for indirect talks.

“Although the issue of direct negotiation between the two sides has been rejected, it has been stated that the path of indirect negotiation is open,” Pezeshkian said during a cabinet meeting. “In that response, direct negotiations have been rejected, but regarding indirect talks, Iran has always been involved in such talks, and the Supreme Leader has emphasized that indirect talks can still continue.”

While Tehran consistently denies seeking nuclear weapons, the UN’s nuclear watchdog estimates Tehran possesses enough enriched material for more than a dozen nuclear weapons. Trump has repeatedly characterized the situation as urgent, warning just days ago that “bad, bad things” would happen without a nuclear agreement.