Secretary of the United States Department of Homeland Security Kirstjen Nielsen leaves after talking with US President Donald Trump

In this AFP file photo taken on October 12, 2017, US President Donald Trump clasps hands with Kirstjen Nielsen after nominating her to be the next Homeland Security Secretary in the East Room of the White House in Washington, DC.

Secretary of the United States Department of Homeland Security has quit her post after talking with President Donald Trump.

The president made the announcement Sunday, adding that US Customs and Border Protection (CBP) Commissioner Kevin McAleenan would replace Homeland Security Secretary Kirstjen Nielsen, who "will be leaving her position."

"I have confidence that Kevin will do a great job," Trump said.

Nielsen herself took to Twitter to also announce she would step down.

"Its [sic] been an honor of a lifetime to serve with the brave men and women of @DHSgov. I could not be prouder of and more humbled by their service, dedication, and commitment to keep our country safe from all threats and hazards," she said, adding in a letter to Trump that, "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 also called on "the brave and dedicated men and women of @DHSgov," saying she was "eternally grateful and proud of what you do each and every day [sic] to protect our homeland."

"Our missions as a Department are vast and have never been more vital," Nielsen wrote. "You are in the arena- keep up the good fight. Thank you for your sacrifices and those of your families. God bless you and God bless our great country."

Her departure comes at a time the administration claims there is a “crisis” at the US southern border to influx of migrants from central and South America.

The development also come in the wake of Trump’s failure to build his promised wall on the border.

Frustrated with the situation at the border, Nielsen met with Trump at the White House to quit her position.