The inspector general for the U.S. intelligence community met privately Thursday with the House Permanent Select Committee on Intelligence amid an escalating dispute over a whistleblower complaint about a phone call between President Trump and an unnamed foreign leader.

The whistleblower is an intelligence officer who was concerned about representations Trump made to the foreign leader, two U.S. officials tell TIME. The officials did not say when the call took place or the topic of the conversation.

News of the complaint emanating from the phone call was first reported by the Washington Post.

U.S. intelligence agencies are authorized to monitor the calls of certain foreign leaders in order to collect intelligence on the “activities and intentions of a foreign power,” the official says. During one of those calls, according to the official, President Trump made “certain representations concerning U.S. policy” during the call that the whistleblower “found troubling.”

An attorney for the whistleblower declined to comment.

Democrats in Congress have demanded that Trump’s top intelligence official hand over a copy of the whistleblower’s complaint. But so far, Trump’s acting Director of National Intelligence, Joseph Maguire, had refused to do so.

The Intelligence Community’s Inspector General, Michael Atkinson, received the complaint on Aug. 12 and passed it to Maguire on Aug. 26, according to Schiff’s letter to Maguire. The Director of National Intelligence is legally required to submit a complaint from the IG to the requisite oversight committee within days, but House Intelligence Chairman Adam Schiff said he has not received it. Schiff said on Thursday that the Department of Justice was involved in the decision to withhold the information from Congress, but has not gotten an answer about the White House’s involvement.

Neither the White House nor the Department of Justice immediately responded to a request for comment.

Atkinson told Schiff about the existence of the complaint on Sept. 9. “Although I believe and appreciate that the Acting DNI is acting in good faith,” Atkinson wrote to Schiff, “[his] treatment of the complainant’s alleged ‘urgent concern’ does not appear to be consistent with past practice.”

Schiff requested the complaint and all related documents from Maguire’s office the following day, but Maguire declined to provide it. On Sept. 13, Schiff announced he had subpoenaed the documents. The disregard for the law, Schiff wrote, had led to the committee to conclude “that the serious misconduct at issue involves the President of the United States and/or other senior White House or administration officials.”

Schiff said that if Maguire did not hand over the complaint by Sept. 17, he would be summoned to a public hearing. But Maguire balked. “The complaint here involves confidential and potentially privileged matters relating to the interests of other stakeholders within the Executive Branch. Any decision by the DNI concerning potential accommodations of the Committee’s requests will necessarily require appropriate consultations,” Jason Klitenic, the general counsel for the DNI’s office, wrote in a letter to Schiff obtained by the New York Times.

Schiff announced Wednesday evening that Maguire would testify publicly before the committee on Sept. 26. Atkinson met with the committee behind closed doors on Thursday, although members said the focus of the briefing was not the substance of the complaint. “We do not have the complaint, we do not know whether the press reports are accurate or inaccurate about the contents of that complaint,” Schiff said.

Both Maguire and Atkinson will appear before the Senate Intelligence Committee next week, according to a committee aide, who would not disclose the exact timing.

Trump defended himself on Twitter Thursday, calling the reports about the whistleblower “Fake News,” and saying that he understands that “virtually anytime” he talks on the phone with a foreign leader, U.S. and foreign agencies may be listening. “No problem!” Trump wrote.

Write to Alana Abramson at Alana.Abramson@time.com.