Updated

President Trump took to Twitter late Monday to issue a stern warning to Iran that an assassination attempt or attack against the U.S. in retaliation for the airstrike that killed Gen. Qassem Soleimani earlier this year would be met with a counterattack that “will be 1,000 times greater in magnitude.”

Speaking hours later in an interview with "Fox & Friends" on Tuesday morning, Trump repeated the warning: "We're all set," he said. "They'll be hit a thousand times harder." 

Trump cited recent reports that claim Tehran is considering an assassination attempt on Lana Marks, the United States’ ambassador to South Africa. U.S. officials have been aware of threats against the ambassador since the spring, but intelligence suggests those threats have become more specific in recent weeks.

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An intelligence source told Fox News the intel community is taking the threat against the ambassador seriously and believe the Iranian regime potentially has the ability to act on an assassination plot. She is just one of several U.S. officials that American intelligence agencies believe Tehran is considering for retaliation for the killing of Soleimani. Iran has denied the reports.

The Pentagon said Soleimani “was actively developing plans to attack American diplomats and service members in Iraq and throughout the region.”

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Late last year, after approving the raid that killed Islamic State leader Abu Bakr al-Baghdadi, Trump said the U.S. will hunt down its enemies anywhere in the world.

Fox News' Andrew O'Reilly,  Gillian Turner, Frank Miles and the Associated Press contributed to this report