"If they do 'assassinate President Trump,' which is always a possibility, I hope that America obliterates Iran, wipes it off the face of the Earth — If that does not happen, American Leaders will be considered 'gutless' cowards!" he wrote on his social media platform, Truth Social.
Trump made the remarks alongside a brief video of Israeli prime minister Benjamin Netanyahu bringing up alleged Iranian plots against Trump in his address to the US Congress on Wednesday.
US media reported last week that the US Secret Service had increased security for Trump weeks ago after authorities learned of an Iranian plot to kill him, although it was not linked to the recent attempt on his life in which a 20-year-old American fired shots during a campaign rally.
CNN reported that US authorities received intelligence from a "human source" on a plan by Tehran targeting the former president, causing protection to be boosted for Trump. Other US outlets also reported the plot.
But it was not connected to the campaign shooting in Butler, Pennsylvania, in which gunman Thomas Matthew Crooks opened fire, lightly wounding Trump and killing a rally attendee, they said.
Relations between Washington and Iran have long been strained and reached a breaking point as Tehran sought revenge for the 2020 killing of Revolutionary Guards commander Qasem Soleimani, ordered by Trump when he was president.
The US National Security Council said it had been "tracking Iranian threats against former Trump administration officials for years."
Trump's post recalled a controversial episode in 2019 when, as president, he threatened the "obliteration" of Iran if the country carried out an attack on "anything American."
That confrontation came after Iranian officials said the path to diplomacy between the two nations was permanently closed after Trump's new round of sanctions Monday.
As president, he also threatened North Korea with "fire and fury like the world has never seen," although he later became friends with the isolated country's dictator, Kim Jong Un, and often referred to their "love."
