The Senate confirmed President Trump's pick to lead the Department of Homeland Security after John KellyJohn Francis KellyMORE left the agency for his White House post earlier this year.
Nielsen, 45, developed a reputation for fierce devotion to Kelly as his deputy at the White House, and before that as his chief of staff at the Department of Homeland Security, which he ran from January until July.
Trump pledged during his presidential campaign to build a U.S-Mexico border wall.
Nielsen said at her confirmation hearing last month that climate change is a crucial issue and said the Trump administration is revising its climate models to better respond to rising sea levels.
A confirmation vote on her nomination is expected later this week, the report added. Some in Congress still have their doubt about the politics behind the move and whether she has what it takes to lead DHS.
"I can't unequivocally state it's caused by humans", she said.
"Ms. Nielsen will be charged with leading the department at a critical time", he said. Though no GOP senators sided against her, the outcome reflected both intense opposition to Trump as well as doubts about Nielsen's executive leadership experience and willingness to challenge the White House in the event of a disagreement.
She also condemned white nationalism, rejected Islamophobia and promised to make cybersecurity a top priority. DHS has 22 subagencies, including everything from immigration enforcement, transportation security, disaster preparedness and response to the Secret Service and the Coast Guard.
Nielsen previously served on George W. Bush's homeland security council.
"It has been an honor to serve as the Department's Acting Secretary, and I look forward to working alongside Ms. Nielsen as her deputy as we continue to carry out the DHS mission of safeguarding the American people, our homeland, and our values", she said in a statement. But Nielsen told the Senate's homeland security panel that "there is no need for a wall from sea to shining sea".
The Trump administration announced in September it would end the program, which allows undocumented immigrants brought into the country as children to live and work.