Iran’s supreme leader, Ayatollah Ali Khamenei, 86, warned on Sunday that any attack by the US would spark a “regional war” in the Middle East and further escalate tensions, as President Donald Trump threatened militarily strikes against the Islamic Republic.

Khamenei’s comments are the most-direct threat he’s made so far as aircraft carrier USS Abraham Lincoln along with associated American warships arrived in the Arabian Sea after Tehran’s bloody crackdown on nationwide protests. While it remains unclear if Trump would use force, the US President has repeatedly said that Iran wants to negotiate and has brought up Tehran’s nuclear program as another issue he wants to see resolved.