US Homeland Security Secretary Kirstjen Nielsen, who oversaw President Donald Trump’s bitterly contested immigration policies during her tumultuous 16-month tenure, resigned on Sunday amid a surge in the number of migrants at the border with Mexico.
A senior administration official said Mr Trump asked for Nielsen’s resignation and she gave it.
“Secretary of Homeland Security Kirstjen Nielsen will be leaving her position, and I would like to thank her for her service,” Mr Trump tweeted.
He added that US Customs and Border Protection Commissioner Kevin McAleenan would become acting secretary.
Ms Nielsen’s departure was first reported by CBS News.
In a tweet late Sunday, Ms Nielsen said that she would stay on until Wednesday.
“I have agreed to stay on as Secretary through Wednesday, April 10th to assist with an orderly transition and ensure that key DHS missions are not impacted,” she said.
Her resignation was the latest high-profile departure from the Trump administration and leaves just four women in his Cabinet. Among others, Mr Trump currently lacks a permanent secretary of defence or chief of staff.