US Homeland Security Secretary Kirstjen Nielsen resigns
Migration continues to frustrate Trump administration despite rise in border arrests
US Homeland Security Secretary Kirstjen Nielsen resigned on Sunday as the administration grows increasingly frustrated with the number of Central American families crossing the US-Mexican border.
President Donald Trump acknowledged her work in a tweet and announced US Customs and Border Protection Commissioner Kevin McAleenan would take over as acting head of the department.
Mr McAleenan is an experienced border official who is well respected within the administration. Ms Nielsen, 46, said in a tweet that she would remain in situ until Wednesday to ease the transition.
The decision to appoint an immigration officer to the post reflects Mr Trump's priority for Homeland Security, which was founded to battle terrorism after 9/11.
Although his aides were considering a staff shake-up at the department, Ms Nielsen's resignation was unexpected.
She travelled to the US-Mexican border on Friday with Mr Trump to take part in talks with border officers and local police.
She echoed Mr Trump's concerns about the situation at the border, although she left the room without explanation while Mr Trump spoke.
As they toured a section of newly rebuilt barriers, Ms Nielsen introduced Mr Trump to local officials.
She returned to Washington, as Mr Trump continued on a fund-raising trip to California and Nevada.
But sources in Washington said Ms Neilsen had grown frustrated by what she considered to be a lack of support from other departments and increased meddling by Mr Trump's aides.
There was no controversy in Ms Neilsen's resignation letter, unlike those written by other officials who left the administration.
"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," she wrote.
"I hope that the next secretary will have the support of Congress and the courts in fixing the laws that have impeded our ability to fully secure America's borders and which have contributed to discord in our nation's discourse."
There was tension between the White House and Ms Nielsen from the moment she became secretary in 2017, replacing John Kelly, who became the White House Chief of Staff.
Some officials regarded Ms Nielsen as being resistant to some of the harshest immigration measures supported by Mr Trump and his aides, particularly senior adviser Stephen Miller, on matters that included the border and protected status for some refugees.
Tensions flared again, as Mr Trump sought to regain control of the immigration debate for his 2020 re-election campaign.
Migrant arrests at the southern border have increased rapidly in recent months, with border agents expected to make 100,000 arrests and denials of entry in March, more than half of which are families with children.
Ms Neilsen pushed Mr Trump's immigration policies, including funding for his border wall, and defended the administration's separation of children from parents.
She told a Senate committee the removal of children from parents facing criminal charges was common practice in the US.
But she was also instrumental in ending the policy, while she abandoned long-standing regulations that dictated how long children are allowed to be held in immigration detention, and requested bed space from the US military for about 12,000 people to try to detain all families who crossed the border.
Centres are currently at capacity, with space for about 3,000 families.
Updated: April 8, 2019 01:22 PM