President Donald Trump said in a Sept. 20 Fox News interview that he is deciding whether to escalate the U.S. war with Iran, warning that “very big things” could happen if Iran does not comply with his demands.

“My question is, if and when do I blow the entire nation up? They better behave,” said Trump during the interview.

Trump also said he is open to meeting Iranian President Masoud Pezeshkian during the United Nations General Assembly in New York.

He has previously threatened major military action against Iran during the conflict, which began with U.S. and Israeli strikes on Feb. 28, but those proposed escalations have not occurred, USA Today has reported.

Iran’s military warned that any new attack would lead to sustained retaliation against U.S. bases and interests, while its parliament speaker said Iran would continue both fighting and negotiating.

Trump’s latest comments echo an April threat in which he warned of devastating consequences for Iran.