The National Endowment for the Humanities has canceled most of its grant programs and started putting staff on administrative leave, as its resources are set to be redirected toward supporting President Trump’s priorities.

Starting late Wednesday night, state humanities councils and other grant recipients began receiving emails telling them their funding was ended immediately. Instead, they were told, the agency would be “repurposing its funding allocations in a new direction in furtherance of the president’s agenda.”

“Your grant’s immediate termination is necessary to safeguard the interests of the federal government, including its fiscal priorities,” the letters said. “The termination of your grant represents an urgent priority for the administration, and due to exceptional circumstances, adherence to the traditional notification process is not possible.”

The letters, more than a half dozen of which were viewed by The New York Times, were on agency letterhead and bore the signature of Michael McDonald, a longtime N.E.H. official who became acting director of the agency last month, after the previous leader, a Biden appointee, was pressed to resign.

In a meeting on Thursday afternoon, Mr. McDonald told senior leadership that upward of 85 percent of the agency’s hundreds of current grants were to be canceled, according to two people privy to the meeting. He also suggested that, going forward, the agency would focus on patriotic programming, the employees said.

Late Thursday, employees began receiving notices that they were being put on administrative leave.

A spokesman for the agency did not respond to a request for comment. The White House referred inquiries to a spokesman for the Office of Management and Budget, which declined to comment.