The White House rejected a request from the House Oversight Committee to hand over documents and make officials available for interviews for a probe into how Jared Kushner got a security clearance, Congressional Democrats announced Tuesday.

White House Counsel Pat Cipollone wrote a bombastic March 4 letter to House Oversight Committee Chairman Elijah Cummings (D-MD), saying that the executive branch would not answer “legally unsupportable ultimatums demanding unilateral surrender of the prerogatives of a co-equal branch of the government.”

Cummings had demanded documents related to how the White House was processing security clearances. The chairman reiterated the request last week after a bombshell report from the New York Times revealed that president Trump overruled the concerns of the CIA to give Kushner, his son-in-law, a security clearance.

Cipollone claimed in the letter that Cummings had failed to establish a “legitimate legislative purpose” for the request, which included the investigative files of “numerous individuals whom the President has chosen as his senior advisors.”

The White House’s refusal to produce documents marks the first direct oversight-related confrontation since Democrats took control of the House at the beginning of the year, and could set the stage for further refusals.

Cummings said in a Tuesday statement that the committee would determine its “next steps in the matter” but stressed that the issue is important to the committee.

“There is a key difference between a president who exercises his authority under the Constitution and a president who overrules career experts and his top advisors to benefit his family members and then conceals his actions from the American people,” he said in the statement.