WASHINGTON (AP) — The White House is again directing former employees not to cooperate with a congressional investigation, this time instructing former aides Hope Hicks and Annie Donaldson to defy subpoenas and refuse to provide documents to the House Judiciary Committee.

The letters from the White House to the Judiciary panel are the latest effort by the White House to thwart congressional investigations into President Donald Trump . Trump has said he will fight "all of the subpoenas" as Democrats have launched multiple probes into his administration and personal financial affairs.

House Judiciary Chairman Jerrold Nadler issued subpoenas for documents and testimony from Hicks, former White House communications director, and Donaldson, a former aide in the White House counsel's office, last month. Both are mentioned frequently in special counsel Robert Mueller's report , along with former White House Counsel Donald McGahn. The White House has also directed former McGahn to refuse to provide documents or testify before the committee.

In directing witnesses not to comply, the White House cited executive privilege over documents and testimony, invoking the power to keep information from the courts, Congress and the public to protect the confidentiality of the Oval Office decision-making process.

But that only extends so far. Nadler said in a statement Tuesday that, while the White House had instructed the former aides not to turn over materials, Hicks had agreed to turn over documents related to her time on Trump's presidential campaign. Those materials are not covered by executive privilege.

Nadler said he thanked Hicks for "that show of good faith." But it was unclear how much material the committee would receive.

The committee is arguing that the documents would not be covered by executive privilege if they left the White House months ago.

"The president has no lawful basis for preventing these witnesses from complying with our request," Nadler said. "We will continue to seek reasonable accommodation on these and all our discovery requests and intend to press these issues when we obtain the testimony of both Ms. Hicks and Ms. Donaldson."

The subpoenas also demanded that Hicks appear for a public hearing on June 19 and that Donaldson appear for a deposition on June 24. They have not yet said whether they will do so.

As the White House has pushed back on the investigations, some Democrats have ramped up their calls for Nadler to open an impeachment inquiry, arguing it would improve congressional standing in the courts as they try to enforce subpoenas. But House Speaker Nancy Pelosi has so far resisted such calls, preferring a slower, more methodical effort.

As part of that approach, the House is expected next week to hold McGahn and Attorney General William Barr , who has refused to turn over the full Mueller report, in contempt of Congress. The resolution scheduled for a June 11 vote will allow the Judiciary Committee to seek court enforcement of its subpoenas.

Nadler has also said that his panel will launch a series of hearings on "the alleged crimes and other misconduct" in Mueller's report as Democrats try to keep the public's focus on his findings in the Trump-Russia investigation.

The hearings will serve as a stand-in of sorts for Mueller, who said last week he would prefer not to appear before Congress and would not elaborate on the contents of his report if he were forced to testify.

The first hearing, on June 10, looks at whether Trump committed obstruction of justice by intervening in the probe. It will feature John Dean, a White House counsel who helped bring down Richard Nixon's presidency, though he served a prison term for obstructing justice.

Democrats have suggested they will compel Mueller's appearance if necessary, but it's unclear when or if that will happen. Negotiations over Mueller's testimony are ongoing.