As feds continue to seek interview with Prince Andrew, Attorney General William Barr says Jeffrey Epstein probe marches on

The federal investigation into convicted sex offender Jeffrey Epstein and his alleged co-conspirators is marching forward -- with or without Prince Andrew's cooperation, according to Attorney General William Barr.

In an exclusive interview with ABC News, Barr said the Justice Department continues to gather evidence in connection with the case, including the pursuit of an interview with the British royal.

"Definitely the department wants to talk to Prince Andrew, that's why the Southern District has been making efforts to communicate and to arrange an interview with him," Barr said. "The department is communicating with him and made it clear that we'd like to interview him."

Federal prosecutors in New York have formally requested testimony from Prince Andrew as part of its criminal investigation into the alleged co-conspirators of Epstein, two officials familiar with the matter told ABC News last month. Prince Andrew is being sought as a witness and is not the target of the investigation, ABC News previously reported.

Geoffrey Berman, the then-U.S. attorney in the Southern District of New York, slammed Prince Andrew's failure to cooperate with investigators last month.

"If Prince Andrew is, in fact, serious about cooperating with the ongoing federal investigation, our doors remain open, and we await word of when we should expect him," Berman said.

Prince Andrew's legal team, however, maintains the prince has consistently offered to cooperate with the federal investigation. They issued a statement last month clarifying their position, saying the prince had "on at least three occasions this year offered his assistance as a witness to the DOJ."

According to a source familiar with the situation, the Department of Justice approached the prince in early January 2020 asking for his cooperation, and his lawyers promptly responded by opening discussions regarding how Andrew would provide his testimony. They were left "slack jawed" when Berman announced on Jan. 27 that the prince had offered "zero co-operation," as they thought they were in mid-negotiation with the prosecutors.

Both sides are remaining tight-lipped on the intricacies of these pre-testimony discussions leaving many baffled as to why there is such a divergence in opinion on the prince's willingness to cooperate.

And in response to news of Maxwell's arrest and a further appeal for his testimony by the acting attorney for the Southern District of New York, Audrey Strauss, a source close to Prince Andrew told ABC News his team "remains bewildered," adding that they have "twice communicated with the DOJ in the last month, and to-date, we have had no response."

Whether Prince Andrew agrees to an interview, investigators continue their work, Barr said. Last week, FBI agents arrested Ghislaine Maxwell, the former companion of Epstein.

From at least 1994 to 1997, Maxwell allegedly assisted, facilitated and contributed to Epstein's alleged abuse of minor girls, a six-count indictment claimed. On Monday, she arrived in New York, where she was transferred to the Metropolitan Detention Center in Brooklyn.

Nearly one year after Epstein's suicide in federal custody, Barr said he remains "livid" -- and made assurances that Maxwell would not meet the same fate.

Barr said he has asked those responsible for her safety to relay, "specifically the protocols they're following, and we have a number redundancy systems to monitor the situation."

"I believe very strongly in that case and I was very proud of the work done by the department, the Southern District, on that case," Barr said.

"And as you will recall, after he committed suicide I said that I was confident that we would continue to pursue this case vigorously and -- pursue anyone who's complicit in it," he continued. "And so I'm very happy that we were able to get Miss Maxwell."

Maxwell is scheduled for a remote detention hearing July 14.