Iran’s top security official says Tehran is considering 13 revenge scenarios against the US for the targeted killing of Lieutenant General Qassem Soleimani.

“Even the weakest of the 13 revenge scenarios will be a historic nightmare for America,” said Ali Shamkhani, the secretary of Iran's Supreme National Security Council (SNSC), Tasnim reported Tuesday.

“For the time being, due to certain considerations, we cannot provide the media with any further information,” Shamkhani said, but added that the revenge process will not be a “one-off operation.”

Shamkhani said that decision-making process will be based on security and international considerations.

The Iranian official said that a total of 19 US military bases — including 11 head bases located east and west of Iran in addition to eight bases in the north and south of Iran — are already on high alert, adding that “we are aware of the conditions of their military equipment and monitoring the smallest developments” there.

“If the American forces do not leave our region vertically, we will make their bodies go horizontally,” he warned.

Iran’s Foreign Minister Mohammad Javad Zarif said on Tuesday that the countdown has begun for the US’s exit from the Middle East. He warned of a war that would last for generations if the region continued to rely on America’s presence.

US President Donald Trump ordered a US drone strike early Friday on General Soleimani’s motorcade upon his arrival in the Iraqi capital at the invitation of the Baghdad government.

The attack also killed Abu Mahdi al-Muhandis, the second-in-command of Iraq’s Popular Mobilization Units (PMU), as well as eight other Iranian and Iraqi people.

Iran has sworn “harsh revenge” against the US for its terrorist operation.

Earlier on Tuesday, the Iranian Parliament amended an earlier counter-terrorism law and designated the Pentagon and all subsidiaries terrorists, in an apparent effort to give the government and the Armed Forces a free hand to prepare for revenge.

On Sunday, Iraqi lawmakers used an extraordinary parliamentary session to vote on a resolution requiring the government to press Washington and its allies to withdraw their troops from Iraq.