Federal prosecutors on Friday declined to make public transcripts of recorded conversations between Michael Flynn and Russia’s ambassador to the United States in December 2016, despite a judge’s order.

In a court filing Friday, the Justice Department wrote that it did not rely on such recordings to establish Flynn’s guilt or determine a recommendation for his sentencing.

Prosecutors also failed to release an unredacted version of portions of the Mueller report related to Flynn that the judge had ordered be made public.

Flynn, who served briefly as President Trump’s first national security adviser, pleaded guilty to lying to the FBI about his conversation with Russian Ambassador Sergey Kislyak, and he cooperated with special counsel Robert S. Mueller III’s investigation. He is awaiting sentencing.

The government’s unusual response came after U.S. District Judge Emmet G. Sullivan in Washington ordered earlier in May that the Justice Department make public various materials related to the case, including transcripts of any audio recordings of Flynn, such as his conversations with Russian officials.

Prosecutors provided one item that Sullivan ordered be released: a transcript of a voice mail left by an attorney for Trump, much of which had already appeared in Mueller’s report. It is unclear how the judge will react to the government’s noncompliance with other elements of his order. Late last year, Sullivan postponed Flynn’s sentencing after angrily lambasting the former national security adviser for his actions, saying, “Arguably, you sold your country out.”

While Flynn’s interactions with Kislyak were described in Mueller’s report and in court documents, the exact words the two men used have not been revealed. U.S. officials have not publicly confirmed the existence of recordings, which are classified.

Sullivan made clear he wanted the full transcript of Flynn’s calls to be shared with the public, although he did not provide his reasoning. The Justice Department’s response appeared to duck that order.

Prosecutors Brandon L. Van Grack of the Justice Department’s national security division, who was formerly on Mueller’s team, and Assistant U.S. Attorney Deborah Curtis of Washington provided little explanation as to why they were not turning over the transcripts but indicated that the judge had asked for material that was not relevant to Flynn’s eventual sentencing.

In a single line addressing Sullivan’s order, prosecutors wrote that the government “is not relying on any other recordings, of any person, for purposes of establishing the defendant’s guilt or determining his sentence, nor are there any other recordings that are part of the sentencing record.”

Sullivan’s request was atypical, some legal experts said, in that he demanded the release of classified records that prosecutors did not use to prove Flynn’s guilt.

Still, some former prosecutors said the government’s response was also notably spare.

“I’m sure they spent a ton of time thinking about how to do this — to protect intelligence equities, to protect their case, to try not to annoy the judge, to balance all those interests,” said Barbara McQuade, a former U.S. attorney in Michigan.

She noted that although there was no public indication that prosecutors had filed additional material under seal, it was possible that they did.

“If they’re simply trying to avoid the order by sidestepping it and saying ‘it’s not necessary to your sentencing decision,’ judges tend not to be satisfied with such a response,” she added.

The U.S. attorney’s office in Washington declined to comment.

The transcripts of the Flynn-Kisylak calls would provide a rare glimpse into the power of American surveillance to capture the private discussions of foreign emissaries — and an intimate look at a budding relationship between a top Russian official and one of the president-elect’s most trusted lieutenants in the weeks before Trump took office.

Flynn’s lying about his contacts with the Russian ambassador made him the shortest-serving national security adviser in U.S. history: He spent just 24 days in the prestigious White House job.

Sullivan ordered the transcripts of Flynn’s conversations released two weeks ago after The Washington Post filed a motion seeking the release of redacted and sealed documents in the case. The Post argued that the public deserved to know more about the Trump adviser’s role in key events and the information he shared with investigators.

As part of his order, Sullivan had also given the government until Friday to release an unredacted version of portions of Mueller’s report dealing with Flynn.

In declining to release that, prosecutors wrote that the “limited remaining redactions pertain to sourcing of information, such as references to grand jury subpoenas.”

They provided no explanation other than to say that “all of the information in the Report that the defendant provided to the Special Counsel’s Office has been unredacted, as has all of the information in the Report that others provided about the defendant.”

The one item that the Justice Department made public on Sullivan’s order was a full transcript of a voice mail that John Dowd, a private attorney for Trump, left for Flynn lawyer Robert Kelner in November 2017.

Most of the voice mail was quoted in Mueller’s report, which described a message left by a personal counsel to Trump for a Flynn attorney after the former national security adviser began to cooperate with investigators. The special counsel scrutinized the message as part of his investigation into whether Trump sought to obstruct the Russia investigation.

The Trump counsel was Dowd, according to people familiar with the episode.

In the voice mail to Kelner, Dowd described himself as “sympathetic.”

“I understand your situation, but let me see if I can’t state it in starker terms,” he said, adding that if “there’s information that implicates the President, then we’ve got a national security issue.”

“So you know, ...we need some kind of heads up,” he added. “Um, just for the sake of protecting all our interests if we can, without you having to give up any...confidential information....remember what we’ve always said about the President and his feelings toward Flynn and, that still remains.”

In a statement Friday, Dowd said there was never anything improper about his contact with Flynn’s lawyer and that he had never tried to discourage Flynn’s cooperation with the government.

“This is clearly a baseless, political document designed to smear and damage the reputation of counsel and innocent people,” Dowd said of the special counsel report.

Devlin Barrett and Spencer S. Hsu contributed to this report.