Donald Trump suffered another resignation last night when Homeland Security Secretary Kirstjen Nielsen quit amid frustration about the crackdown on the border.

President Donald Trump immediately replaced her with Customs and Border Protection Commissioner Kevin McAleenan, a longtime border official who is well-respected by members of Congress and within the administration.

Trump aides had been eyeing a staff shake-up at Homeland Security and had already withdrawn the nomination for another key immigration post but Ms Nielsen’s resignation came as a surprise.

She travelled to the US-­Mexico border on Friday with Mr Trump to participate in a round-table with border officers and local law enforcement. There she echoed Mr Trump’s comments on the situation at the border. As they toured a section of newly rebuilt barriers, Ms Nielsen was at Mr Trump’s side, introducing him to local officials.

Privately, she had grown increasingly frustrated by what she saw as a lack of support from other departments and increased meddling by Trump aides, sources said.

She went into a meeting with Mr Trump yesterday not knowing whether she’d be fired or would resign, and she ended up resigning.

Mick Mulvaney. Photo: REUTERS22
Mick Mulvaney. Photo: REUTERS

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 in 2017. Ms Nielsen was viewed as resistant to some of the harshest immigration measures supported by the president and his aides, particularly senior adviser Stephen Miller, both around the border and on other matters like protected status for some refugees.

Once Mr 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.

In recent weeks, as a new wave of migration taxed border resources and Mr Trump tried to regain control of the issue for his re-election campaign, tensions flared anew.

Meanwhile, Mr Trump’s current chief of staff has insisted the president’s tax returns will never be handed over to Democratic politicians.

The defiant stance by Mick Mulvaney flies in the face of an effort in Congress to learn more about the real estate mogul’s personal finances.

Asked on ‘Fox News Sunday’ whether congressional Democrats would succeed in obtaining the Republican president’s tax returns, Mr Mulvaney said: “No, never. Nor should they.”