Speaking to reporters at a House briefing on election security, Nielsen was asked about the 2017 intelligence community report that found Putin not only "ordered an influence campaign" aimed at the 2016 presidential election, but also that Putin had a "clear preference" for Trump in those meddling efforts.
Nielsen's remarks, which come amid her reported tensions with Trump over immigration, sparked instant condemnation.
After the briefing, Nielsen was asked about intelligence agencies' conclusions that Moscow used social media, leaks of hacked emails and other tactics in 2016 in an attempt to help Trump beat Hillary Clinton.
However, Nielsen also said she had no reason to question any intelligence findings and added that Russian Federation did try to influence U.S. voters and will continue to do it in the future.
"I do believe that Russian Federation did and will continue to try to manipulate Americans' perspective on a whole variety of issues", Nielsen said. Nielsen said she was unaware of that assessment, which has been public for over a year.
The U.S. intelligence community said in a January 2017 assessment that Russian Federation had tried to influence the election to benefit Trump.
Nielsen's comments come as top intelligence officials say Russian Federation is likely to meddle again and the Department of Homeland Security is working with states to improve election security ahead of the 2018 midterms.
Amazon explains that recorded Echo conversation
The woman called Amazon to complain, and the company apologized for the mistake, saying it takes privacy concerns very seriously. A private conversation of a couple in the USA was recorded by Alexa and then sent to a random person in their contact list.
With political primaries already underway and the November midterm elections fast approaching, top national security officials briefed members of Congress on Tuesday about gaps in election security.
"Do you have any reason to doubt the January 17th  Intelligence Committee assessment that said it was [Russian President] Vladimir Putin who tried to meddle in this election to help President Trump?". All three agencies agree with this judgment.
After Nielsen's remarks Tuesday, DHS press secretary Tyler Houlton released a statement saying, "The Secretary has previously reviewed the Intelligence Community's assessment and agrees with it - as she stated today and previously", adding, "Russian goals included undermining faith in the U.S. democratic process and harming a candidate's electability and potential presidency". "No, there are not tanks in the streets, but what's happening right now goes to the heart of who we are as a nation, and I say this not as a Democrat who lost an election but as an American afraid of losing a country".
She stopped short of saying Russian Federation tried to sway the 2016 election in Donald Trump's favor. "Russian goals included undermining faith in the US democratic process and harming a candidate's electability and potential presidency".
Indeed, the ongoing investigation of Russia's meddling in the 2016 USA election has made it hard for Trump to wrap his arms around Putin.
"The Secretary has previously reviewed the intelligence community's assessment and agrees with it - as she stated today and previously", he said in a statement.
"Despite the short time frame they had to prepare it, the intelligence community did a very good job with the ICA", said Vice Chairman of the Senate Select Committee on Intelligence Senator Mark Warner (D-VA). They claimed in their report that the intelligence community didn't follow its best practices when it concluded Russian Federation favored Trump in the election.