President Trump on Monday ordered the Justice Department to declassify significant materials from the investigation of Russian interference in the 2016 election, threatening to spur a showdown with federal law enforcement officials resistant to publicizing information from an ongoing probe.

In a statement, the White House said Trump was ordering the department to immediately declassify portions of the secret court order to monitor former campaign adviser Carter Page, along with all interviews conducted as officials applied for that authority.

Trump also instructed the department to publicly release the unredacted text messages of several former high-level Justice Department and FBI officials, including former FBI director James B. Comey and deputy director Andrew McCabe.

For months, conservative lawmakers have been calling on the department to release Russia-related and other materials, many of them accusing law enforcement of hiding information that might discredit the investigation now led by special counsel Robert S. Mueller III.

Trump was sympathetic — though he had shied from using his formal declassification power to force Justice Department officials to hand over documents they otherwise would not have. His doing so Monday significantly raises the stakes.

The Justice Department had turned over thousands of pages of materials to Congress, though its leaders had made clear there was a line they would not cross because making some materials public might put sources at risk or harm an ongoing investigation.

The latest standoff is further complicated by the fact that the public announcement of the order came before the Justice Department received instructions about what specific material it was supposed to cover, according to a person familiar with the matter.

The department said in a statement: “When the President issues such an order, it triggers a declassification review process that is conducted by various agencies within the intelligence community, in conjunction with the White House Counsel, to seek to ensure the safety of America’s national security interests. The Department and the Federal Bureau of Investigation are already working with the Director of National Intelligence to comply with the President’s order.”

Rep. Adam B. Schiff (Calif.), the ranking Democrat on the House Intelligence Committee, called the order a “clear abuse of power” and said that based on his conversations with federal law enforcement officials, the FBI and Justice Department would consider the release of these materials “a red line that must not be crossed as they may compromise sources and methods.”

“This is evidently of no consequence to a President who cares nothing about the country and everything about his narrow self-interest,” Schiff said in a statement.

But Rep. Mark Meadows (R-N.C.) and others who have called for the release of the material praised the move.

“Transparency wins,” Meadows said in a tweet. “This is absolutely the right call from @POTUS. It’s time to get the full truth on the table so the American people can decide for themselves on what happened at the highest levels of their FBI and Justice Department.”

The White House said in a statement that Trump’s order came at the request of “a number of committees of Congress” and was done “for reasons of transparency.” Earlier this month, conservative lawmakers had made a public appeal to Trump directly to release all the materials at issue.

In addition to ordering the release of materials on Page, Comey and McCabe, the president ordered the department to declassify interviews with Justice Department official Bruce G. Ohr, who worked in the deputy attorney general’s office and had conversations with the author of a dossier alleging ties between the Trump campaign and Russian officials.

Trump also ordered the release of text messages written by FBI officials Peter Strzok and Lisa Page. Strzok and Page were both involved in the Russia probe, as well as the investigation into Hillary Clinton’s use of a private email server.

“These documents will reveal to the American people some of the systemic corruption and bias that took place at the highest levels of the DOJ and FBI, including using the tools of our intelligence community for par­tisan political ends,” said Rep. Matt Gaetz (R-Fla.).

The list of those whose text messages Trump said should be released — Comey, McCabe, Strzok, Lisa Page and Ohr — includes officials who have long been targets of the president’s ire.

Trump fired Comey as FBI director, saying the Russia case was on his mind when he did so. Mc­Cabe and Strzok were fired later — McCabe after he was accused of lying about a media disclosure, Strzok for sending anti-Trump text messages to Lisa Page.

Representatives for all five either declined to comment or could not be reached Monday night.

Former officials said the president’s action was troubling and seemed to be politically motivated.

“This order is an unprecedented misuse of the President’s declassification authority for purely political reasons and manifests a dangerous disregard for the protection of information developed in sensitive counterintelligence investigations,” said David Laufman, a former chief of the Justice Department’s Counterintelligence and Export Control Section who had been involved in the Russia case. “Given the Administration’s intensified efforts to identify and prosecute leakers of classified information, it’s also more than a little ironic.”

The Justice Department already has released thousands of texts from Lisa Page and Strzok, and it has also made public a heavily redacted version of its application for a Foreign Intelligence Surveillance Court order to monitor Carter Page.

David S. Kris, a former assistant attorney general for national security who is now at the Culper Partners consulting firm, said the release of the surveillance order was “totally unprecedented.”

Trump “has the authority to do this, but here, as in so many other areas, his exercise of authority is tainted by a severe conflict of interest, as he is a subject of the investigation to which these [orders] pertain,” he said.

The Justice Department is no stranger to confrontations with conservative lawmakers and even the White House over making materials public. It is possible officials could reach an ­agreement with the White House about what should and should not be released that would satisfy all sides.

In May — in a meeting brokered by the White House — Justice Department and FBI officials sat down with senior lawmakers to discuss the bureau’s use of a confidential source in the Russia case. The move seemed to mollify lawmakers, at least for a time.

But the confrontation has been escalating again. Deputy Attorney General Rod J. Rosenstein said publicly earlier this year that the department “is not going to be extorted” in the battle over congressional access to secret records. Some conservatives later introduced articles of impeachment against the Justice Department’s No. 2 official, though House Speaker Paul D. Ryan (R-Wis.) then said he opposed their efforts.

Trump has at times seemed to be close to firing senior law enforcement officials, including Attorney General Jeff Sessions and Rosenstein, though he has never made good on his private threats. Mueller is investigating, among other things, Trump’s efforts to pressure Justice Department leaders as part of his inquiry into whether the president sought to obstruct justice.

Shane Harris contributed to this report.