One of the accused men hasn't been arrested and is believed to be in Iran.
Prosecutors say the plan dates back to September, before the Presidential election. They allege that an unnamed official in Iran’s paramilitary Revolutionary Guards planned to carry out surveillance and kill Mr Trump.
Investigators learned of the plot while interviewing Farhad Shakeri, an Afghan national identified by officials as an Iranian government agent, who was deported from the US after being imprisoned on robbery charges. He told investigators that a Revolutionary Guard contact in Iran instructed him to assassinate Mr Trump, according to the criminal complaint.
Two other men who the authorities say were recruited to participate in other assassinations, including a prominent Iranian-American journalist, have been arrested.
Donald Trump has a history of animosity towards Iran and the allegations raise questions about [how] this will affect his policy towards the country in his new Presidency.
Jane Hill presents BBC News at Ten reporting by Sarah Smith and James Landale.
