US President Donald Trump fired on Monday US Acting Attorney General Sally Yates for refusing to enforce his order suspending immigration from seven Muslim-majority nations, the White House said in a press release.

Earlier in the day, Yates, interim successor to Loretta Lynch, released a letter, ordering the Department of Justice (DOJ) to resist defending President Donald Trump’s executive order on refugees in court, citing constitutional concerns.

"At present, I am not convinced that the defense of the executive order is consistent with these responsibilities nor am I convinced that the executive order is lawful," the letter stated. "[The] Department of Justice will not present arguments in defense of the executive order."

Following the move, Trump terminated Yates, whom he inherited from President Barack Obama.

“The acting Attorney-General Sally Yates has betrayed the Department of Justice by refusing to enforce a legal order designed to protect the citizens of the United States,” the release stated on Monday.

Dana Boente, US Attorney for the Eastern District of the state of Virginia was named Acing Attorney General until Trump's nominee Senator Jeff Sessions is confirmed by the Senate, the White House added.

“I am honored to serve President Trump in this role until Senator Sessions is confirmed. I will defend and enforce the laws of our country to ensure that our people and our nation are protected,” Boente said in the statement.