WASHINGTON — The White House said Thursday that it has fired a member of the Surface Transportation Board, a move that comes as the independent federal regulatory agency is considering the proposed merger of Union Pacific and Norfolk Southern railroad companies.

“Earlier this evening, I received an email from the White House purporting to terminate my position at the Surface Transportation Board,” Robert Primus wrote in a post to LinkedIn on Wednesday. “This is deeply troubling and legally invalid.”

Primus’ termination, which was first reported by The Wall Street Journal, comes as the White House has increasingly moved to exert control over agencies across the federal government, including those considered to be independent.

Primus said in his post that he planned to “continue to discharge my duties as a member of the Board and, if I’m prevented from doing so, I will explore my legal options.”

The Presidential Personnel Office — which is now set to be run longtime Trump aide Dan Scavino — did not offer a reason for Primus’ dismissal, according to a copy of the email seen by MSNBC. Staff member Mary Sprowls said that his position as a member was terminated “effective immediately.” Access to Primus’ government devices was shut off on Wednesday evening, according to a person familiar with matter.

Reached for comment, a White House spokesperson did not provide a specific reason for Primus’ firing.

“Robert Primus did not align with the President’s America First agenda, and was terminated from his position by the White House,” White House spokesperson Kush Desai said in a statement. “The ministration intends to nominate new, more qualified members to the Surface Transportation Board in short order.”

MSNBC has reached out to the Surface Transportation Board for comment.

The Surface Transportation Board began the regulatory review process for the proposed railway merger in July, after Union Pacific announced that it would acquire Norfolk Southern at a price tag of $85 billion.

The deal, which would create the nation’s first transcontinental railroad, is still under review by the board. The proposal has faced pushback from labor unions and sparked controversy over its potential impact on competition in the railroad industry.

Primus’ term was set to end in 2027, according to the board’s website. He was first confirmed to the board in the final months of President Donald Trump’s first term, and he became the chairman during the Biden administration. The Trump administration appointed a new member as chairman at the start of his second term.

Before joining the Surface Transportation Board, Primus worked with several Democratic members of Congress.

The Trump administration has increasingly moved to exert more control over agencies, working to oust officials who the White House deems insufficient to carry out the president’s agenda. Earlier this week, Trump announced he was moving to fire Federal Reserve governor Lisa Cook, although Cook’s attorneys said she would sue.

On Wednesday, the Trump administration fired Centers for Disease Control and Prevention Director Susan Monarez, prompting several other top health officials to exit the agency in protest.

In January, Trump fired two Democratic commissioners at the Equal Employment Opportunity Commission. In March, he fired two Democratic commissioners at the Federal Trade Commission. In May, Trump fired the Librarian of Congress, moving on days later to fire the head of the U.S. Copyright Office.