WASHINGTON — House Intelligence Committee Chairman Adam Schiff, D-Calif., said Thursday that he believed it was likely that President Donald Trump or his aides were working to keep the details of an urgent complaint by an intelligence community whistleblower from Congress.

"I believe that there is an effort to prevent this information getting to Congress, and if the assertion is accurate that the Department of Justice has made and the DNI has affirmed that this involves a potentially privileged communication, then at one level or another, it likely involves either the president or people around him," Schiff told reporters following a closed-door briefing with the intelligence community’s inspector general, Michael Atkinson, and the Intelligence Committee’s members that lasted several hours.

A congressional source tells NBC News that Atkinson declined to reveal to lawmakers the substance of the whistleblower complaint that NBC News and others have confirmed pertains to a phone call by the president.

The news was first reported by The New York Times. Trump has denied the allegation.

Atkinson, a former career Justice Department lawyer who was appointed by Trump and confirmed by the Senate, believed the complaint should be turned over to Congress, but was overruled, according to documents made public in recent days.

“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 following the closed-door session. "But what I do know is this: If, in a matter within the jurisdiction of the director of national intelligence, you have an employee of that community or a contractor or a detailee [who] follows the law, makes the complaint, and it is possible for the subject of that complaint to essentially botch the complaint or keep it from Congress, then this system is badly broken."

Schiff said that Atkinson had not been authorized to disclose the information to the lawmakers because his boss, the director of national intelligence, has taken the position that the complaint does not fall under the Intelligence Community Whistleblower Protection Act, which requires that “urgent concern” complaints about intelligence matters be turned over to Congress.

Lawyers for the acting director of national intelligence, Joseph Maguire, consulted with the Justice Department’s Office of Legal Counsel in making that determination, a DOJ official acknowledged to NBC News.

The Senate Intelligence Committee expects to be briefed next week by both Maguire and Atkinson on the whistleblower complaint. Maguire is also scheduled to testify next Thursday in a public session of the House Intelligence Committee.

“We’re determined to do everything we can to determine what this urgent concern is, to make sure that the national security is protected and to make sure that this whistleblower is protected,” Schiff said.

Schiff read one line from one of the letters from Atkinson about the whistleblower’s complaint that stated the subject matter involved "not only falls within the director of national intelligence’s jurisdiction but relates to the most significant and important of the director of national intelligence’s responsibilities to the American people.”

“This is what’s being withheld from Congress right now,” Schiff said.

Asked what type of action might be taken to obtain the contents of the complaint, the chairman said that Democrats are exploring their options with House general counsel, including legal ones.

“We will have a very good case to seek a mandatory restraining order,” he said, giving one example. “It’s not a situation where we can afford to go through weeks or months of litigation in this court or that court — there’s an urgency here that I think the courts will recognize.”