In reaction to President Donald Trump’s tweet this morning that said “Iran is playing with fire,” Iranian civilian and military officials doubled down on their defiance of U.S. and international demands to curb their controversial missile program, which Washington says violates U.N. Security Council Resolution 2231.

 “Mr. Trump has tweeted that he issued a warning to Iran. [People] bigger than you had warned Iran but couldn’t do anything,” said Mohsen Rezaei, the head of Iran’s Expediency Discernment Council and former chief of the Islamic Revolution Guards Corps (I.R.G.C.).

During Friday prayers across the country, senior Iranian clerics also emphasized that the Islamic Republic will defy U.S. and international pressure. “America should understand that Iran will not negotiate with anyone regarding its missile activity and defense power,” said Ayatollah Alireza Erafi, the Friday Prayer leader of Iran’s holy city of Qom. Ayatollah Abdolnai Namazi, Friday Prayer leader of Kashan city in Isfahan Province, warned Washington and its allies that they will “regret considering military option against Iran.”

Iran’s Foreign Minister Javad Zarif also stressed that Tehran is “unmoved by threats” and will not stop its missile program. “We will never use our weapons against anyone, except in self-defense. Let us see if any of those who complain can make the same statement,” he wrote on his official account.

But Zarif’s pledge fails to assuage U.S. and regional states’ growing concern when I.R.G.C. leaders, who are in charge of Iran’s military affairs and regional policies, publicly threaten to attack Israel and Arab countries. When Iran test-fired two ballistic missiles last March, one of them had “Israel should be wiped off the Earth” inscribed on it in Hebrew.