Department of Homeland Security Secretary Kirstjen Nielsen testifies before a House Homeland Security Committee hearing on “The Way Forward on Border Security” on Capitol Hill in Washington, U.S., March 6, 2019.
Department of Homeland Security Secretary Kirstjen Nielsen testifies before a House Homeland Security Committee hearing on “The Way Forward on Border Security” on Capitol Hill in Washington, U.S., March 6, 2019.

Embattled U.S. Homeland Security Secretary Kirstjen Nielsen was forced out rather than resigning willingly, several U.S. news outlets are reporting.

Nielsen submitted her resignation Sunday night after meeting at the White House with President Donald Trump, who almost daily has voiced his anger at the thousands of undocumented Central American migrants crossing the southern U.S. border with Mexico to seek asylum in the United States.

The news accounts say Nielsen had no intention of quitting when she arrived to meet with the U.S. leader, but that he was determined to ask for her resignation, which she submitted shortly after the meeting.

FILE - A van carrying asylum seekers from the bord
FILE - A van carrying asylum seekers from the border is escorted by security personnel as it arrives to immigration court, in San Diego, California, March 19, 2019.

Immigration hardliners in the White House, including National Security Advisor John Bolton and immigration policy advisor Stephen Miller, had been pushing Trump to oust her, viewing her as not tough enough to deal with the crisis at the border.

Trump announced that current U.S. Customs and Border Protection Commissioner Kevin McAleenan will replace Nielsen, becoming the acting secretary of the Department of Homeland Security, with Nielsen staying on through Wednesday in a brief transition.

"I have confidence that Kevin will do a great job," Trump said.

In Twitter comments, Trump twice contended that the United States has no room for more arriving immigrants.

Last week, Trump retreated from a days-long threat to close the U.S.-Mexico border after advisors told him that a closure would have a significant negative impact on the U.S. economy, the world's largest. Instead, he said Mexico had a year to curb the surge of migrants and interdict the flow of illicit drugs into the U.S. or else he would impose tariffs on automobiles Mexico exports to the U.S.

"Mexico must apprehend all illegals and not let them make the long march up to the United States, or we will have no other choice than to Close the Border and/or institute Tariffs," Trump said.

Also last week, Trump rescinded his nomination of Ronald Vitiello as the new Immigration and Customs Enforcement chief, saying he wanted to go "in a tougher direction."

Nielsen was the Homeland Security secretary for 16 months, overseeing the controversial separation of thousands of migrant children from their parents as they arrived at the border, a policy overturned in a court decision. She also secured an agreement with Mexico to start processing U.S. asylum requests while the immigrants were still in Mexico.

U.S. Department of Homeland Security Secretary Kir
FILE - Then-Department of Homeland Security Secretary Kirstjen Nielsen visits U.S. President Donald Trump's border wall in the El Centro Sector in Calexico, California, Oct. 26, 2018.

U.S. officials say the immigration crisis has worsened in recent weeks, with frequent complaints from Trump. He declared a national emergency to build a barrier wall along an increasing expanse of the border, tapping funding from various government programs after Congress refused to fund wall construction. Sixteen states and other groups have filed suit to contest his action, but the dispute has not been resolved.

Faced with declining support within the White House, Nielsen submitted her resignation, saying in a letter to Trump, "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."

While she did not say exactly why she is quitting, Nielsen wrote she hopes the next secretary "will have the support of Congress and the courts in fixing the laws which have impeded our ability to fully secure America's borders and which have contributed to discord in our nation's discourse. Our country and the men and women of DHS deserve to have all the tools and resources they need to execute the mission entrusted to them."

U.S. President Donald Trump participates in a roundtable discussion on immigration and border security at the U.S. Border Patrol Calexico Station before visiting the U.S.-Mexico border in Calexico, California, April 5, 2019.
Trump Visits US-Mexico Border to Inspect Replaced Border Wall
U.S. President Donald Trump has visited the U.S. Border Patrol Calexico Station, a crossing point between the United States and Mexico.In a room full of Border Patrol agents, congressmen and members of his administration, Trump praised the progress made keeping people out of the country by way of the border wall in the area."The system is full," Trump said of the nation's immigration system. "We have to say, 'We're sorry, we can't take you.' We're going to look at that and look at it very, very…

Trump has expressed frustration with the situation along the southern border, where hundreds of thousands of migrants trying to escape poverty and crime in Guatemala, El Salvador and Honduras have traveled through Mexico in hopes of entering the United States. Under U.S. law, foreign nationals are allowed to apply for asylum.

White House sources have said Trump often yelled at Nielsen for apparently not being strong enough in curbing the number of migrants trying to enter the United States.

House Speaker Nancy Pelosi called the Trump administration's immigration polices "cruel" and said they "have only worsened the humanitarian suffering at the border."

"It is 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," Pelosi said in a statement. "America needs a Homeland Security Secretary who will respect the sanctity of families, honor our proud heritage as a nation of immigrants, and restore sanity to this Administration’s policies," she said.

FILE - In this June 20, 2018, file photo, immigran
FILE - In this June 20, 2018, file photo, immigrant children walk in a line outside the Homestead Temporary Shelter for Unaccompanied Children, a former Job Corps site that now houses them in Homestead, Florida.

Nielsen faced a public outcry over the administration's highly unpopular policy of separating migrant families when they crossed into the U.S.

Thousands of young children were taken from their parents and held in separation facilities. Nielsen was responsible for executing that policy while at times denying such a policy existed.

Despite the acrimony, Nielsen wrote, "I can say with confidence our homeland is safer today than when I joined the Administration. We have taken unprecedented action to protect Americans."

Trump thanked Nielsen for her service.