Last Wednesday, senior FBI and national intelligence officials relayed an urgent message to the White House: Information being sought by House Intelligence Committee Chairman Devin Nunes could endanger a top-secret intelligence source.

Top White House officials, with the assent of President Trump, agreed to back the decision to withhold the information. They were persuaded that turning over Justice Department documents could risk lives by potentially exposing the source, a U.S. citizen who has provided intelligence to the CIA and FBI, according to multiple people familiar with the discussion and the person’s role.

The showdown marked a rare moment of alignment between the Justice Department and Trump, who has relentlessly criticized Attorney General Jeff Sessions and other top Justice officials for the probe into Russia’s interference in the 2016 election led by special counsel Robert S. Mueller III.

But it is unclear whether Trump was alerted to a key fact — that information developed by the intelligence source had been provided to the Mueller investigation.

The debate over the risk to the source is now at the center of a pitched battle between House Republicans and the Justice Department.

After the White House sided with the department’s decision to refuse the request, Nunes (R-Calif.) publicly vented his frustration, saying Sunday that he may try to hold Sessions in contempt for refusing to comply. He said that his classified-document request and subsequent subpoena to the Justice Department did not refer to an individual.

“They are citing spurious national security concerns to evade congressional oversight while leaking information to The Washington Post ostensibly about classified meetings,” he said in a statement to The Post. “Congress has a right and a duty to get this information and we will succeed in getting this information, regardless of whatever fantastic stories the DOJ and FBI spin to the Post.”

Several administration officials said they fear Trump may reverse course and support Nunes’s argument.

White House officials did not respond to requests for comment.

For the intelligence agencies, Nunes’s request threatened to cross a red line of compromising sources and methods of U.S. intelligence-gathering, according to people familiar with their views. Intelligence officials fear that providing even a redacted version of the information Nunes seeks could expose that person and damage relationships with other countries that serve as U.S. intelligence partners.

The role of the intelligence source in the Mueller investigation may now be seized upon by conservative Republicans who have publicly accused the Justice Department and intelligence agencies of overreach and misuse of their surveillance powers.

Some have alleged that officials within the government have worked against Trump, and they have criticized Deputy Attorney General Rod J. Rosenstein, who oversees the special counsel probe, for refusing to let members of Congress see a “scope memo” outlining the people and issues under investigation by Mueller.

Last month, House allies of Trump drafted articles of impeachment against Rosenstein as a “last resort” if he does not provide Congress with more information.

[Trump-allied House conservatives draft articles of impeachment against Rosenstein as ‘last resort’]

It’s not clear what documents Nunes requested in his classified April 24 letter to the Justice Department. He told reporters this week that he is investigating the FBI’s abuse of the Foreign Intelligence Surveillance Act “and other matters.”

Because Sessions is recused from the Russia investigation and investigations involving the 2016 campaign, he is not involved in the discussions surrounding Nunes’s request, according to a person familiar with the matter.

During a meeting at the White House last Wednesday, senior FBI and intelligence officials told Chief of Staff John F. Kelly that turning over the information could contradict years of policy about protecting intelligence sources, according to three people familiar with the matter. The people who described the meeting include those who support the release of the information and those opposed to it.

Kelly then consulted with Trump, who agreed it was important to protect intelligence sources, according to a person with knowledge of the conversation.

Assistant Attorney General Stephen E. Boyd laid out those concerns to Nunes in a letter the following day, noting that the department made the decision after “consultations” with the White House and intelligence agencies.

“Disclosure of responsive information to such requests can risk severe consequences including potential loss of human lives, damage to relationships with valued international partners, compromise of ongoing criminal investigations, and interference with intelligence activities,” Boyd wrote.

Nunes told reporters Monday that the Justice Department’s stance was “awfully suspicious,” suggesting that the White House did not share the department’s concerns.

“The word that comes to me is obfuscation,” he said.

On Tuesday, House Speaker Paul D. Ryan (R.-Wis.) said he had not discussed the matter with Nunes but added that he expected congressional subpoenas to be enforced.

“We expect the administration to comply with our document requests,” Ryan said.

The Justice Department has been sparring with lawmakers and congressional committees for months over document requests related to the FBI investigations. In most instances, officials have turned over materials.

At one point, Nunes had threatened to impeach top Justice Department officials when they did not immediately hand over an unredacted document detailing the origin of the investigation into whether the Trump campaign coordinated with Russia to influence the 2016 election. The department later gave Nunes access to a version with modest redactions, and Nunes thanked Rosenstein for his cooperation.

[Justice Dept. gives Nunes access to document on Russia probe’s origins, cooling his threat to impeach its leaders]

Rosenstein has sought to make clear in recent weeks that while he is willing to compromise, he will go only so far. Last week, in response to the revelation that members of the conservative House Freedom Caucus drafted articles of impeachment, Rosenstein declared that the Justice Department was “not going to be extorted” and would not hand over documents that might harm national security or ongoing investigations.

“If we were to just open our doors to allow Congress to come and rummage through the files, that would be a serious infringement on the separation of powers, and it might resolve a dispute today, but it would have negative repercussions in the long run, and we have a responsibility to defend the institution,” Rosenstein said.

Josh Dawsey, Karoun Demirjian and Matt Zapotosky contributed to this report.