And though Defense Secretary Mark Esper tweeted Monday that the U.S. is working with “our partners to address this unprecedented attack,” a lack of allies on the world stage has complicated the likelihood of an intervention by America’s armed forces.

“I don’t want war with anybody. I’m somebody that would like not to have war,” Trump said Monday, while also cautioning that the U.S. is “prepared more than anybody” to retaliate.

But Trump appeared defensive Tuesday evening of his approach toward Tehran after Sen. Lindsey Graham (R-S.C.) tweeted that the White House’s “measured response” to the shooting down an American drone in June “was clearly seen by the Iranian regime as a sign of weakness.”

Trump responded online: “No Lindsey, it was a sign of strength that some people just don’t understand!”

The president adopted a more aggressive tone Wednesday afternoon, refusing to rule out a military strike and even threatening “the ultimate option,” full-blown war with Iran.

“There’s plenty of time to do some dastardly things. It’s very easy to start,” he told reporters in Los Angeles, adding: “I think we have a lot of good capital. If we have to do something, we’ll do it without hesitation.”

Secretary of State Mike Pompeo echoed that hardline rhetoric Wednesday before arriving in Saudi Arabia for talks with Crown Prince Mohammed bin Salman.

“This is an attack of a scale we’ve just not seen before,” he told reporters, according to Reuters. “The Saudis were the nation that were attacked. It was on their soil. It was an act of war against them directly.”

Iran on Monday delivered an ominous message to U.S. officials through the Swiss Embassy in Tehran, denying involvement in the attack and “warning that in case of any aggression against the Islamic Republic, Iran’s response will be prompt and strong and it may include broader areas than the source of attacks,” the Mehr News Agency reported.

The memo communicated that “the Islamic Republic’s reaction will be rapid and crushing and will likely target more extensive areas than the origin of the attack,” Iran’s state-run Fars News also reported.

While Pompeo explicitly condemned Iran on Saturday for having “launched an unprecedented attack on the world’s energy supply,” Trump’s more equivocal assessment of Iranian guilt earlier this week — paired with his apparent deference to the Saudi government in his weekend social media posts — provoked some consternation in Congress.

Still, Trump has repeatedly suggested in recent days that Iran was behind the attack in Saudi Arabia, remarking Monday that “certainly it would look” as though Tehran was responsible and accusing its leadership of promulgating “a very big lie” in relation to the destruction of the American drone earlier this summer.

Col. Turki al-Maliki, a Saudi military spokesman, showed journalists at a news conference in Riyadh on Wednesday the remains of Iranian cruise missiles and drones he alleged were deployed in the attack on the kingdom’s facilities, according to the Associated Press.

“The attack was launched from the north and was unquestionably sponsored by Iran,” he said, contradicting the Iranian-backed Houthi rebels in Yemen who have claimed credit for the assault. Iran and Iraq are situated to the north of Saudi Arabia, while Yemen is located to the south.

Trump’s order Wednesday to hike sanctions on Iran comes as the Islamic Republic already faces punishing economic penalties the administration has leveled since withdrawing last year from the 2015 multinational nuclear deal.

Tensions have escalated and diplomacy has steadily deteriorated between Tehran and Washington, with a potential meeting between Trump and Iranian President Hassan Rouhani now unlikely to take place on the sidelines of the United Nations General Assembly later this month.

Rep. Liz Cheney (R-Wyo.) said Wednesday she applauded the president’s latest sanctions maneuver, but called for a “proportional military response” to the attack in Saudi Arabia.

“It’s got to be a response that is significant enough that it lets the Iranians know that this sort of attack on the global oil supply won’t be accepted, that it won’t go unanswered,” Cheney, the chairwoman of the GOP conference, told reporters. “The Iranians have to understand that the United States is serious about our commitment to our allies.”

Melanie Zanona contributed to this report.