National Security Adviser Robert O'Brien explained to “Fox & Friends” on Thursday why he believes Iran and Russia allegedly tried to interfere with the 2020 elections.

“It’s no surprise that Iran has done this,” O'Brien said, citing the fact that because Trump has pulled the U.S. out of the Joint Comprehensive Plan of Action, Iran been “cut off” from “billions of dollars of the jackpot that they received when they signed the JCPOA.”

The Iran nuclear deal framework – officially the JCPOA – was a historic agreement reached by Iran and several world powers, including the U.S., in 2015, under Barack Obama’s presidency.

Three years later, President Trump announced that he would be pulling the U.S. out of the Iran nuclear deal, calling the agreement “defective at its core.”

“All those billions have been cut off so there’s no surprise that they’re getting involved in our election,” O'Brien said. “They don’t like the fact that the Abraham Accords were signed and that Israel’s making peace with all their Arab neighbors so it’s no surprise there with Iran.”

“The same thing with Russia,” he continued, adding that “the president’s been tougher on Russia than any administration since Ronald Reagan.”

“We see that they’re out on Twitter and various places with disinformation,” O'Brien said. “You can see the same thing with China.”

“China goes about trying to cultivate local leaders, mayors and governors and congressmen and convince them that if they don’t vote China’s way or they don’t do what China wants, China won’t invest in their districts or their cities and that sort of thing,” he explained.

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O'Brien added that “there are other countries that are attempting to do things via cyber and Twitter and Facebook.” He noted that intelligence officials have not yet disclosed that information publicly.

“So what we ask the American people to do is just make sure that the information you get is from a trusted source,” he stressed.

O'Brien made the comments the morning after Director of National Intelligence John Ratcliffe said at an FBI press conference that Iran and Russia are attempting to sway the 2020 elections and have obtained some voter registration information.

Ratcliffe noted on Wednesday night that both nations had taken specific actions to influence voters' opinions. He said that the registration information they obtained could be used to confuse voters through false communication. 

The Iranian interference that's been discovered, Ratcliffe said, has been designed to incite social unrest and damage the president.

The news conference was held as Democratic voters in at least four battleground states, including Florida and Pennsylvania, have received threatening emails, falsely purporting to be from the far-right group Proud Boys, that warned “we will come after you” if the recipients didn’t vote for President Trump.

The voter-intimidation operation apparently used email addresses obtained from state voter registration lists, which include party affiliation and home addresses and can include email addresses and phone numbers. Those addresses were then used in an apparently widespread targeted spamming operation. The senders claimed they would know which candidate the recipient was voting for in the Nov. 3 election, for which early voting is ongoing.

Host Brian Kilmeade noted on Thursday that “both Russian President Vladimir Putin and Iran have denied any involvement in this.”

“We’re taking major steps to protect the elections,” O'Brien said.  I’ve held over 20 high-level meetings here at the White House with The National Security Council.”

“The Department of Homeland Security is working with our 50 secretary of states across the country,” he continued. “We have National Guard stood up with their cyber units.”

He also noted that “We spent hundreds of millions of federal dollars helping secretaries of state and lieutenant governors, who manage their elections out in their states, harden their infrastructure.”

“So across the country, we’re making big efforts to ensure that our election infrastructure is hardened and that people when they go out to vote, they know their vote’s going to be counted,” he added.

On Wednesday, noting that his agency was responsible for investigating election crimes, FBI Director Christopher Wray vowed to take action in order to ensure the integrity of U.S. elections. He said that Americans should be "confident" that their votes count.

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“The good news is we’re so decentralized,” O'Brien said, explaining that “95% of the ballots that are cast have some sort of paper analog so that they can be audited.”

“It’s very difficult for an adversary to actually change the outcome of the elections, and we’ve been doing everything we can to make sure that’s the case on Election Day, that no one can play with the tallies, with the votes as they come in,” he continued.

Fox News’ Sam Dorman and The Associated Press contributed to this report.