Donald Trump's homeland security secretary, Kirstjen Nielsen, dramatically quit her post on Sunday night, becoming the latest in a series of high-profile figures to leave his administration.
Ms Nielsen's departure was confirmed by the President on Twitter and came after she met Mr Trump at the White House.
Secretary of Homeland Security Kirstjen Nielsen will be leaving her position, and I would like to thank her for her service....
— Donald J. Trump (@realDonaldTrump) April 7, 2019
It is understood Mr Trump was unhappy with her performance at Homeland Security as he moved towards taking a tougher line on immigration.
Only last week, speaking in Las Vegas, the US president declared that "our country is full" as he placed immigration firmly on the agenda of his re-election campaign.
According to reports in Washington, the final straw came when Ms Nielsen was blindsided by the White House decision to rescind the nomination of Ronald Vitello as head of Immigration and Customs, one of the most senior officials in her department.
Ms Nielsen's tenure since succeeding John Kelly as Homeland Security Secretary in December 2017 has been uncomfortable.
In May last year, she reportedly offered her resignation after she was upbraided over immigration by Mr Trump in front of cabinet colleagues, but was dissuaded from doing so by Mike Pence, the vice president.
The Department of Homeland Security denied the report in the New York Times, and Ms Nielsen then issued a statement in which she sought to play down the reported rift.
"The President is rightly frustrated that existing loopholes and the lack of Congressional action have prevented this administration from fully securing the border and protecting the American people," she said. "I share his frustration."'
Read more: Kirstjen Nielsen quits as US Homeland Security Secretary