Editor's Note: This article originally appeared on Business Insider.

Iran has discussed 13 “revenge scenarios” that could be a “historic nightmare” for the United States following the killing of Maj. Gen. Qasem Soleimani, an Iranian national security official reportedly said.

Citing a report from Iran's Fars News Agency, Reuters reported that Ali Shamkhani, the secretary of Iran's Supreme National Security Council, said on Tuesday that “the Americans should know that until now 13 revenge scenarios have been discussed in the council, and even if there is consensus on the weakest scenario, carrying it out can be a historic nightmare for the Americans.”

In the days since President Donald Trump ordered the drone strike that killed Soleimani, Iran's most important military leader, late last week, Iran has vowed to enact “severe revenge” over Soleimani's killing, and both countries have traded threats.

Iran's supreme leader, Ayatollah Ali Khamenei, appeared at a meeting of the council in the hours after the strike and called for a direct and proportional hit on the United States, The New York Times reported, citing three Iranians familiar with the meeting.

This would be a starkly different approach for Iran in terms of hostilities with the U.S., in the sense that it typically operates via proxy forces.

Beyond The Times' report, there has been no confirmation that the supreme leader has ordered or would order a direct strike on the US in the region or elsewhere. Iran is outmatched by the US in terms of conventional military capabilities, but a war between the two would likely be detrimental to both sides.

A direct strike on US forces or assets could provoke a harsh response from the US, particularly given that Trump was moved to take out Soleimani because he was worried he looked weak after Iran shot down a US surveillance drone in June, The Washington Post recently reported.

Over the weekend, Trump warned Iran that if it targeted the U.S. he would hit 52 Iranian targets, including “Iranian culture” sites, which could constitute a war crime.

Both Iran and Trump have a history of making intense threats without following through, and it's unclear what comes next.

Meanwhile, Iran's Parliament on Tuesday unanimously voted to classify the entire U.S. military and the Department of Defense as terrorist organizations.

Soleimani was the leader of the elite Quds Force of Iran's Revolutionary Guard. The Trump administration designated the Revolutionary Guard a terrorist organization last year and viewed Soleimani as a terrorist.

Mohammad Javad Zarif, Iran's top diplomat, on Tuesday told NPR that the US committed an act of war and an act of terrorism in taking out Soleimani. The US has moved to block Zarif from traveling to New York City this week to address the United Nations Security Council.

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