Sen. Lindsey Graham, R-SC sent a warning to Iran Tuesday night to de-escalate tensions with the U.S. following a missile strike on Iraqi bases that house U.S. forces.
Appearing on Sean Hannity's show on Fox News Channel, Graham called the missile strike an "act of war by any definition." He also claimed Trump has all the authority he needs under Article II of the U.S. Constitution to respond.
"Let me say tonight if you are watching television in Iran. I just got off the phone with the president. Your fate is in your own hands in terms of the regime's economic viability. (If) you continue this crap, you're going to wake up one day out of the oil business," Graham said.
Iran struck back at the United States for killing Iranian Revolutionary Guard Gen. Qassem Soleimani last week. The death prompted angry calls to avenge his slaying.
Iran fired a series of ballistic missiles at two military bases in Iraq housing American troops. U.S. and Iraqi officials said there were no immediate reports of casualties.
Trump later tweeted "All is well!" and "so far, so good!" -- an indication some speculated to mean that there were no causalities.
Graham claimed Trump does not want regime change in Iran, but "he wants the behavior of the regime to change." Specifically, Graham referred to Iran's ballistic missile program, nuclear program, and allegations that Iran is a state sponsor of terrorism.
Tensions between the two nations have been steadily rising since Trump pulled the U.S. out of a multilateral nuclear deal in May 2018 aimed at curbing Iran's nuclear program, and imposed new economic sanctions. International nuclear inspectors, as recently as March 2019, said that Iran was continuing to comply with the deal, but that changed in recent months. Iran announced Sunday it would no longer adhere to the agreement following Soleimani's assassination.
Graham, who was one of Trump's fiercest critics during the 2016 election cycle, has become one of the president's closest allies although he has disagreed with Trump at times.
The Associated Press contributed to this report.