Iranian Gen. Qassem Soleimani is dead because he miscalculated how President Trump would respond to an impending attack against Americans in Iraq, Sen. Lindsey Graham, R-S.C., said Friday on "Fox & Friends."

"The intelligence was that Soleimani was orchestrating chaos in Iraq at our expense and throughout the region," Graham explained. "The president was informed of these potential attacks and he acted. This was a defensive strike to neutralize future attacks that were planned and executed by Soleimani and the popular mobilization front: the Shiite militias in Iraq."

Graham said Trump acted to prevent "holy hell" from occurring in Iraq and the region and Soleimani did not think the United States would take such a bold action.

"He's not dead today because of what he did in the past, he's dead today because he miscalculated what President Trump would do regarding future attacks," said Graham in a phone interview.

IRAN VOWS 'HARSH RETALIATION' AFTER US AIRSTRIKE KILLS GEN. QASSEM SOLEIMANI

Graham was asked about Iranian President Hassan Rouhani's promise to respond to the airstrike with "harsh retaliation" for the United States' "heinous crime."

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Graham said President Trump must now make it clear to Iran that any such retaliation will put their oil refineries at risk.

"Their oil refineries are the last thing they have in terms of an economy," he said.

Echoing the words of Pompeo, Graham took to Twitter on Thursday night writing that the killing of Soleimani -- who "had American blood on his hands" -- was a "major blow to the Iranian regime."

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"To the Iranian government: If you want to stay in the oil business leave America and our allies alone and stop being the largest state sponsor of terrorism in the world," he continued.

"Doing nothing in this region shows weakness. It emboldens Iran," Secretary of State Mike Pompeo told "Fox & Friends" earlier Friday morning. "We're confident that our strategy...all the things that we have done to create the conditions for a more stable and peaceful and prosperous Middle East...we think this is a part of."

"Iran never won a war, but never lost a negotiation!" the president tweeted on Friday morning.

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"But now, what will change Iran's calculation? How we respond," Graham said.

"They are going to come after us with a vengeance if we do not reset the table quickly," Graham explained. "And, if I were the president, I would put on the table targets in Iran -- not Iraq and Syria. Economic targets that crush the economy."

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Graham said that while the United States' maximum pressure campaign against the Iranian regime has worked, what would "take it to the next level" would be to threaten to "destroy the ability of the Iranians to refine oil and sell it."

"The president has to convince the ayatollah that if he retaliates, our response will be greater than the market will bear," he concluded.