The threat from Iranian operatives has worried current and former administration officials since Iranian General Qasem Soleimani was assassinated on Mr. Trump’s orders in January 2020.

Late last year, federal prosecutors charged an operative of Iran’s Islamic Revolutionary Guard Corps and two U.S.-based people with plotting to surveil and assassinate critics of the Iranian regime. The IRGC operative allegedly told investigators he was pushed by unnamed IRGC officials to plan an attack against Mr. Trump.

For years, U.S. law enforcement and intelligence officials have been concerned about Iran’s ability to direct or inspire attacks within the United States — a concern that has ramped up since Soleimani’s killing. The FBI, Department of Homeland Security and others have devoted significant resources to countering the threat.

There are a range of potential targets. In recent years, prosecutors have charged people with plotting to kill Mr. Trump’s former national security adviser John Bolton and Iranian American journalist Masih Alinejad, both of whom are frequent critics of Iran’s government. Bolton was granted Secret Service protection in 2021, but Mr. Trump revoked his protection this year.