WASHINGTON (AP) -- President Donald Trump fired Federal Reserve Governor Lisa Cook late Monday, a surprise move constituting a sharp escalation in his battle to exert greater control over what has long been considered an institution independent from day-to-day politics.

Trump said in a letter posted on his Truth Social platform that he is removing Cook because of allegations that she committed mortgage fraud. Bill Pulte, a Trump appointee to the agency that regulates mortgage giants Fannie Mae and Freddie Mac, made the accusations last week.

Pulte alleged that Cook had claimed two primary residences -- in Ann Arbor, Michigan and Atlanta -- in 2021 to get better mortgage terms. Mortgage rates are often higher on second homes or those purchased to rent.

The announcement came days after Cook said she wouldn't leave the seven-member Fed board despite Trump previously calling for her to resign. Senate Democrats had expressed support for Cook.

"The Federal Reserve has tremendous responsibility for setting interest rates and regulating reserve member banks. The American people must have the full confidence in the honesty of the members entrusted with setting policy and overseeing the Federal Reserve," Trump wrote in a letter addressed to Cook, a copy of which he posted online. "In light of your deceitful and potentially criminal conduct in a financial matter, they cannot and I do not have such confidence in your integrity."

Trump argued that firing Cook was constitutional, even if doing so will raise questions about control of the Fed as an independent entity.

"The executive power of the United States is vested to me as President and, as President, I have a solemn duty that the laws of the United States are faithfully enacted," the president wrote in the letter to Cook. "I have determined that faithfully enacting the law requires your immediate removal from office."

The firing is likely to touch off a legal battle and Cook could be allowed to remain in her seat while the case plays out. Cook would have to fight the legal battle herself, as the injured party, rather than the Fed.

It is the latest effort by the administration to take control over one of the few remaining independent agencies in Washington. Trump has repeatedly attacked the Fed's chair, Jerome Powell, for not cutting its short-term interest rate, and even threatened to fire him.

Forcing Cook off the Fed's governing board would provide Trump an opportunity to appoint a loyalist. Trump has said he would only appoint officials who would support cutting rates.

Powell signaled last week that the Fed may cut rates soon even as inflation risks remain moderate. Meanwhile, Trump will be able to replace Powell in May 2026, when Powell's term expires. However, 12 members of the Fed's interest-rate setting committee have a vote on whether to raise or lower interest rates, so even replacing the chair might not guarantee that Fed policy will shift the way Trump wants.