Kirstjen Nielsen: US Homeland Security secretary resigns, Trump announces

US homeland security secretary Kirstjen Nielsen has resigned, Donald Trump announced on Twitter.

The president publicly thanked Ms Nielsen for her service in a tweet on Sunday night.

He said that US customs and border protection commissioner Kevin McAleenan would step into the role in the interim.

The reason for Ms Nielsen’s departure is not yet clear. The 46-year-old had held the position since December 2017.

Her resignation later did not contain a hint of controversy, unlike others who have left the Trump 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 which have impeded our ability to fully secure America's borders and which have contributed to discord in our nation's discourse.”

Ms Nielsen travelled to the US-Mexico border on Friday with Mr Trump to participate in a roundtable with border officers and local law enforcement.

There she echoed the president’s comments on the situation at the border, though she ducked out of the room without explanation for some time while Mr Trump spoke.

As they toured a section of newly rebuilt barriers, Ms Nielsen was at Mr Trump’s side, introducing him to local officials.

There have been persistent tensions between the White House and Ms Nielsen almost from the moment she became secretary, after her predecessor, John Kelly, became the White House chief of staff.

She was viewed as resistant to some of the harshest immigration measures supported by the president and his aides, particularly senior adviser Stephen Miller, both on matters around the border and others like protected status for some refugees.

Once General Kelly left the White House last year, Ms Nielsen’s days appeared to be numbered. She had expected to be pushed out last November, but her exit never materialised.

During the government shutdown over Trump's insistence for funding for a border wall, her stock inside the White House even appeared to rise.

But, in recent weeks, as a new wave of migration has taxed resources along the border and as Trump sought to regain control of the issue for his 2020 re-election campaign, tensions flared anew.

During her tenure, Ms Nielsen had to defend a number of Mr Trump’s controversial policies, such as his plan to build a wall on the border with Mexico and the separation of migrant children from their families.

Demonstrators shouted “shame” at Ms Nielsen as she was eating at a Mexican restaurant in Washington, DC, in June, forcing her to leave.

She was a consistent defender of the US president, at one point telling senators she could not remember Mr Trump’s controversial “s***hole countries” remark, which he allegedly made in a meeting she attended.

She also dutifully pushed Mr Trump’s immigration policies, including funding for his border wall, and defended the administration's practice of separating children from parents, although she would later work to end the policy.

Last May, it emerged that she came close to quitting after the president berated her in a cabinet meeting about immigration.

The Department of Homeland Security did not immediately respond to a request for comment.

Agencies contributed to this report