US President Donald Trump on Monday vowed that any attack by Iran would be met with a response "1,000 times greater in magnitude", after reports that Iran planned to avenge the killing of top Iranian General Qassem Suleimani in a drone strike last January. "According to press reports, Iran may be planning an assassination, or other attack, against the United States in retaliation for the killing of terrorist leader Suleimani, which was carried out for his planning a future attack, murdering US troops, and the death & suffering..." Mr Trump said on Twitter after reports emerged on Monday of an alleged Iranian plot to assassinate the US ambassador to South Africa. In a follow-up tweet, the US President said, "Any attack by Iran, in any form, against the United States will be met with an attack on Iran that will be 1,000 times greater in magnitude." A report published yesterday by <em>Politico</em> said US intelligence details an <a href="https://www.thenational.ae/world/mena/iran-considering-plot-to-assassinate-us-ambassador-to-south-africa-officials-say-1.1077294">Iranian plot to assassinate ambassador Lana Marks</a>. Unidentified US government officials told the publication that evidence of the plot had become more specific in recent weeks. Ms Marks, a 66-year-old businesswoman who has known Mr Trump for several decades and is a member of his Mar-a-Lago club in Florida, is aware of the threat against her. She has no known ties to Iran but it is possible her friendship with the US president is a factor for the Iranian government, which operates clandestine networks in South Africa. The plot is believed by officials to be one of several assassination attempts under consideration by the Iranian regime in retaliation for the killing of Suleimani, commander of the Islamic Revolutionary Guard Corps' Quds Force. Relations between Washington and Tehran have been tense since the Iranian revolution in 1979, and have spiralled since Mr Trump took office and pulled the US out of a nuclear deal between Iran and global powers in May 2018. Washington is also pushing to extend an arms embargo on Iran that starts to progressively expire in October as well as reimposing UN sanctions on Iran. The Iranian navy last week said it drove off American aircraft that flew close to an area where military exercises were under way near the Strait of Hormuz. The military said three US aircraft were detected by Iran's air force radars after they entered the country's air defence identification zone. In June last year, a US RQ-4 drone was shot down by Iran after allegedly violating Iranian airspace, a claim the US denied. US Secretary of State Mike Pompeo on Monday declined to comment directly on the reported threat to Ms Marks. But he told <em>Fox News</em> that Iran "has engaged in assassination efforts all across the world. They have assassinated people in Europe and in other parts of the world. We take these allegations seriously". "We make very clear to the Islamic Republic of Iran that this kind of activity – attacking any American any place at any time, whether it's an American diplomat, an ambassador, or one of our service members – is completely unacceptable," he said. An Iranian foreign ministry spokesman on Monday claimed the report of an assassination plot was baseless and part of "repetitive and rotten methods to create an anti-Iranian atmosphere on the international stage".