The messages seemed to originate from an extreme right supportive of Trump gathering and were intended to "impel turmoil", National Intelligence Director John Ratcliffe said.
Mr Ratcliffe likewise said US authorities discovered Iran and Russia had acquired "some citizen enrollment data".
Both Iran and Russia prevented the allegations from getting political decision impedance.
"Iran's solid dismissal of American authorities' dreary, ridiculous and bogus cases was passed on to the Swiss diplomat [who speaks to US interests in Tehran]," Iranian unfamiliar service representative Saeed Khatibzadeh told state TV.
"As we have said previously, it has no effect for Iran who wins the US political race," he included.
Kremlin representative Dmitry Peskov: "We think this is sad. These allegations come each day, they are altogether totally unfounded, they depend on nothing."
"They are in all likelihood a type of inner political cycle associated with the forthcoming decisions."
Mr Ratcliffe's choice to hold an instructions so near the official political decision was viewed as a demonstration of the administration's interests over democratic obstruction and disinformation crusades from unfamiliar entertainers.
The insight boss said Iran's "parody messages" professed to be sent by the extreme right Proud Boys bunch so as to "scare electors, affect agitation and harm" President Donald Trump.
He included that the citizen information could be utilized in endeavors to "impart bogus data to enlisted electors that they expectation will plant disarray tumult and subvert your trust in American popular government".
Mr Ratcliffe said authorities "have not seen similar activities from Russia", yet know they have some elector data.
In numerous states, citizen information is accessible upon demand, however each state has various necessities on who can demand elector data, what information is accessible and how this information may be utilized, as indicated by the National Conference of State Legislatures.
"In the event that you get a scary or manipulative email in your inbox, don't be frightened and don't spread it," Mr Ratcliffe stated, calling the activities to impact US citizens "urgent endeavors by frantic enemies".
This declaration definitely has shades of the 2016 Russian obstruction in the US political decision.
In that political race a huge number of phony bots were made via web-based media claiming to be American citizens.
Leftist PC frameworks were additionally hacked.
From this declaration, however, it's muddled how Iran and Russia got the data - and precisely what information they have.
You just need to take a gander at your spam channel to see that numerous individuals have your email address.
The principle charge against Iran is it has sent "parody messages" to electors in swing states. Assuming valid, this is probably not going to be a refined assault.
In numerous states as well, citizen enlistment data is openly accessible.
What's more, no place in the declaration was there any additional data about how widescale the messages have been.
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FBI Director Christopher Wray joined Mr Ratcliffe at the news gathering. He said that US political decision frameworks were as yet secure and "tough".
"You ought to be sure that your vote checks," Mr Wray said. "Early, unconfirmed cases to the opposite ought to be seen with a solid portion of distrust."
The authorities didn't offer further subtleties on how the citizen information was acquired or what the Russians might be doing with the data.
US insight offices closed in 2016 that Kremlin-upheld programmers were behind a push to subvert Hillary Clinton's official run, utilizing both digital assaults and phony reports planted via online media.
Iran has not figured out how to effectively hack US frameworks.
The messages being referred to were routed to enlisted Democratic electors in a few states, including the important milestone of Florida, and encouraged them to decide in favor of Mr Trump - or there will be consequences.
"You will decide in favor of Trump on Election Day or we will come after you," the messages stated, as per US media.
"Change your gathering connection to Republican to tell us you got our message and will go along."
As of Wednesday, more than 40 million Americans have projected early votes in the official challenge between Mr Trump and Democrat Joe Biden.
