On Sunday, her 16-month tour at Homeland Security came to an end when Nielsen submitted her resignation to the president.
Nielsen initially joined the Trump administration in January 2017 as a an assistant to Trump's first DHS secretary, John Kelly. Customs and Border Protection chief Kevin McAleenan will then become acting secretary of DHS.
House Speaker Nancy Pelosi added it was "deeply alarming that the Trump Administration official who put children in cages is reportedly resigning because she is not extreme enough for the White House's liking".
Making these changes now is an even worse decision, he said, given apprehensions of immigrants at the border are spiking.
He had previously threatened to close the US-Mexico border if Congress and Central American governments did not act to stem a flow of migrants that saw Nielsen last week order an "emergency surge" of personnel to handle the situation.
US count shows no Pakistan F-16s shot down in Indian battle
The news report has come at a time when India has taken up the use of F-16 by Pakistan in the 27 February dogfight. According to Foreign Policy magazine, Pak invited USA to physically count its F-16 planes.
On Friday, he called for Congress to "get rid of the whole asylum system" and get rid of immigration judges, and criticized a long-standing federal court decree mandating certain standards of care for migrant children. Both US and worldwide law prohibit the US from refusing entry to people who are in danger of prosecution in their home countries; both US statute and court settlements offer extra due-process protections to asylum seekers, children, and families. "We do know that he does advocate for border patrol agents and he has been trying to let the American public know of the crisis that's happening on the border", Garza said.
These include the US administration's much-criticised 2018 policy separating parents and children at the US-Mexico border. "He's more pressing for actions at the border that don't respect our treaty obligations, domestic statutes on how we treat people seeking asylum".
"Despite our progress in reforming homeland security for a new age, I have determined that it is the right time for me to step aside", Nielsen said in a resignation letter she later shared on Twitter. "She had a background in cyber security".
"I could not be prouder of and more humbled by their service, dedication, and commitment to keep our country safe from all threats and hazards", she said. "And it, frankly, has to raise the question for anyone who's offered a Cabinet opportunity [from] President Trump, whether their reputation will survive".
"As someone who worked hard to put together bipartisan bills previous year, Congress has tried hard to find pathways to work with this administration that still respects our humanitarian commitments, global legal commitments", said Coons.