Government prosecutors on Thursday released the audio recording of a voicemail from President Donald Trump's then-personal lawyer asking Michael Flynn's attorney for "some kind of heads up" about the former national security adviser's cooperation with investigators.

"Hey, Rob, uhm, this is John again," the Nov. 22, 2017 voicemail recording starts out, as Trump's lawyer, John Dowd, requests Flynn's attorney, Rob Kelner, for a "heads up" about the nature of Flynn's cooperation, a move that special counsel Robert Mueller's team has described as a "potential" effort to hinder the investigation into Russian meddling in the 2016 election.

"If, on the other hand, we have, there's information that. .. implicates the President, then we've got a national security issue, or maybe a national security issue, I don't know ... some issue, we got to-we got to deal with, not only for the President, but for the country," Dowd tells Kelner in the voicemail. "So ... uh ... you know, then-then, you know, we need some kind of heads up. Um, just for the sake of ... protecting all our interests, if we can, without you having to give up any ... confidential information."

Dowd also tells Kelner that he "understand[s]" that Flynn can't join the joint defense agreement with the president, and added that the president's "feelings toward Flynn" "still remains." Flynn and his legal team had an informal joint defense agreement with the president and had engaged in privileged discussions before Flynn withdrew as he started cooperating with prosecutors.

Excerpts from the voicemail were included in Mueller’s report and the government made public a complete transcript of the recording last week.

In court documents filed last month, government prosecutors described the contact from Trump's attorney, as one of many "potential" efforts by those close to the president to thwart the investigation -- an effort exposed because of Flynn's 18 month-long cooperation with the special counsel's team.

"The defendant informed the government of multiple instances, both before and after his guilty plea, where either he or his attorneys received communications from persons connected to the Administration or Congress that could have affected both his willingness to cooperate and the completeness of that cooperation," the government noted in a court filing from last month.

In a statement to ABC News last week when the full transcript was released, Dowd said Mueller's report “suggests that the joint defense conversations attributed to me by voicemail and statements and conclusions by Flynn counsel were an attempt by me to make them reconsider their position to cooperate.”

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

Flynn on Thursday filed motion to drop Kelner as his attorney. Kelner did not respond to ABC News' request for comment.