WASHINGTON (AP) -- Pro-Iran hackers have threatened to release emails supposedly stolen from people connected to President Donald Trump, according to a news report, a move that federal authorities call a "calculated smear campaign."

The United States has warned of continued Iranian cyberattacks following American strikes on Iran's nuclear facilities and the threats those could pose to services, economic systems and companies.

The Cybersecurity and Infrastructure Security Agency said late Monday that the threat to expose emails about Trump is "nothing more than digital propaganda" meant to damage Trump and other federal officials.

"A hostile foreign adversary is threatening to illegally exploit purportedly stolen and unverified material in an effort to distract, discredit, and divide," CISA spokeswoman Marci McCarthy wrote in a social media post, linking to a report from Reuters about the threat. "These criminals will be found, and they will be brought to justice."

Reuters reported that it contacted the alleged hackers online. They told the news organization that it held a large cache of emails from Trump chief of staff Susie Wiles, other top advisers and porn actor Stormy Daniels, to whom a hush money payment led to Trump's criminal conviction.

Federal prosecutors charged three Iranians last year on allegations of hacking into Trump's presidential campaign. Hackers also targeted the campaign of Democrats Joe Biden and Kamala Harris and unsuccessfully tried to leak material supposedly taken from Trump to Democrats and members of the media.

The threat to release more hacked emails was reported the same day that CISA, the FBI and National Security Agency issued a public bulletin warning that hacking groups supportive of Tehran may attack U.S. interests despite a fragile ceasefire between Iran and Israel.

The hackers, authorities warned, could seek to disrupt or disable critical infrastructure systems such as utilities, transportation and economic hubs. They also could target defense contractors or other American companies with ties to Israel, the agencies said.

The bulletin outlined recommendations, including the use of regular software updates and strong password management systems to shore up digital defenses.

Hackers backing Tehran have targeted U.S. banks, defense contractors and energy companies following American strikes on Iranian nuclear facilities -- but so far have not caused widespread disruptions.