US President Donald Trump has ordered a shake-up of the Department of Homeland Security's leadership, the head of the Secret Service says, after the White House declared the official would soon leave his post.
The Secret Service said Randolph "Tex" Alles would depart his job next month, a day after the ousting of Homeland Security Secretary Kirstjen Nielsen, with whom Trump had clashed over immigration.
"No doubt you have seen media reports regarding my 'firing.' I assure you that this is not the case, and in fact was told weeks ago by the administration that transitions in leadership should be expected across the Department of Homeland Security," Alles said to Secret Service agents.
Neither Trump nor the White House has explained the overhaul of DHS, but the president has expressed anger at a recent surge in Central American migrants.
The Republican president made stopping illegal immigration a centrepiece in his run for office in 2016, promising to build a wall on the border with Mexico, and said he'd make border security a key part of his 2020 campaign for re-election.
Senior senators from both parties said they were concerned about a vacuum in leadership at the agency, which also oversees the Secret Service, the Coast Guard, the Federal Emergency Management Agency and the Transportation Security Administration, among other critical functions.
Ron Johnson, the Republican chairman of the Senate Homeland Security Committee, said in a statement that he was "concerned with a growing leadership void within the department tasked with addressing some of the most significant problems facing the nation."
Dianne Feinstein, the top Democrat on the Senate Judiciary Committee, said at least 10 top positions in the department were being filled with acting officials.
White House spokeswoman Sarah Sanders said James Murray, a career Secret Service agent, would take over the agency in May.
Alles had run the Secret Service for two years and served in the US Marine Corps for 35 years before retiring as a major general in 2011.
Alles was the latest in a long list of senior officials to leave the Trump administration, including the secretaries of state, defence, homeland security, interior, veterans affairs and health and human services, the attorney general and numerous senior White House aides.
On Twitter, Trump said Kevin McAleenan, the US Customs and Border Protection commissioner, would become acting DHS secretary.
The White House and DHS did not respond to requests for comment.
Trump in recent weeks empowered his hard-line conservative aide Stephen Miller to lead the administration's border policies, according to CNN.
