The House Select committee investigating the Jan. 6 attack on the Capitol and the White House are ramping up the pressure on former Trump White House Chief of Staff Mark Meadows to cooperate with the probe into the insurrection as the committee zeros in on former president Donald Trump’s inner circle.

White House Deputy Counsel Jonathan Su sent a letter to Meadows’s lawyer, George Terwilliger III, Thursday morning notifying him that President Biden will not assert executive privilege or immunity over the documents and deposition requested by the House Select committee related to his client.

Meadows was subpoenaed by the committee at the end of September. While he has been “engaged” with investigators to negotiate the terms of his deposition and turning over of documents, the pace of these discussions has caused the committee to weigh more aggressive measures against him.

Terwilliger responded Thursday by saying Biden “is the first President to make no effort whatsoever to protect presidential communications from being the subject of compelled testimony. Mr. Meadows remains under the instructions of former President Trump to respect longstanding principles of executive privilege. It now appears the courts will have to resolve this conflict.”

In an emailed statement he said Biden’s position runs “contrary to decades of consistent bipartisan opinions from the Justice Department that senior aides cannot be compelled by Congress to give testimony.”

In his letter, Su acknowledges the importance of “candid advice” from the president’s senior staff but cites “the unique and extraordinary circumstances, where Congress is investigating an effort to obstruct the lawful transfer of power under our Constitution” as reason not “to shield information reflecting an effort to subvert the Constitution itself.”

“Consistent with President Biden’s determination that an assertion of privilege is not justified with respect to testimony and documents relating to these particular subjects, he has determined that he will not assert executive privilege with respect to your client’s deposition testimony on these subjects, or any documents your client may possess that bear on them,” Su writes. “For the same reasons underlying his decisions on executive privilege, President Biden has determined that he will not assert immunity to preclude your client from testifying before the Select Committee.”

The letter will allow the committee to further pressure Meadows to cooperate, although the former chief of staff has the ability to continue to challenge the request in courts.

Last week, the select committee threatened to take more aggressive measures to compel testimony from former Justice Department official Jeffrey Clark after he refused to answer questions Friday during a closed-door interview with the panel. And the committee last month moved to hold Stephen K. Bannon in criminal contempt for failing to cooperate with its subpoena — and has indicated they are willing to hold others who stonewall the committee in criminal contempt.

The House later voted to find Bannon in contempt, referring the decision to the Justice Department, which has yet to announce whether it will prosecute the former White House chief strategist.