The Duke of York, in his role as colonel of the Grenadier Guards, at a memorial in Bruges to mark the 75th Anniversary of the liberation of the Belgian town.

Prince Andrew has reportedly hired a top extradition lawyer in Britain and is refusing to assist federal prosecutors investigating alleged child sex trafficking by his one-time friend Jeffrey Epstein.

Those prosecutors in New York now are considering their "options" for dealing with Andrew, a top official said Monday.

Andrew, a son of Britain's Queen Elizabeth II, claimed in November he was willing to help law-enforcement officials in their investigations of the wealthy investor who killed himself in a federal jail last August while awaiting trial.

But Geoffrey Berman, the U.S. attorney for the Southern District of New York, told reporters on Monday that the Duke of York has ruled out cooperating with investigators from his office.

"Contrary to Prince Andrew's very public offer to cooperate with our investigation into Epstein's co-conspirators, an offer that was conveyed via press release, Prince Andrew has now completely shut the door on voluntary cooperation," Berman said at a press conference.

"And our office is considering our options," said Berman.

It is not clear whether Berman would wd be able to force Andrew's cooperation.

On Friday, the Daily Telegraph in Britain reported that Andrew had hired Clare Montgomery, a lawyer whom the newspaper described as "the leading expert on extradition law."

A spokeswoman for Montgomery's law firm, Matrix Chambers, declined to comment on the Telegraph's report when contacted Monday by CNBC.

Montgomery's clients have include Chile's former dictator Augusto Pinochet in his ultimately successful fight against extradition from Britain on human rights violations charges issed by a Spanish magistrate, as well as fugitive India diamond merchant Nirav Modi in his bid to avoid extradition on fraud and money laundering charges.

And "she has successfully represented a string of prominent Russian citizens who have been the focus of requests from the Russian Federation," according to her biography says on Matrix Chambers's website.

Montgomery also represented the Swedish Judicial Authority in its effort to have WikiLeaks founder Julian Assange extradited from Long to Sweden to face sex assault charges there lodged by two women.

Berman had told reporters in January that "to date, Prince Andrew has provided zero cooperation" to federal law enforcement invesrtigators.

"Jeffrey Epstein couldn't have done what he did without the assistance of others, and I can assure you that the investigation is moving forward," Berman said at the time.

Buckingham Palace has not responded to Berman's comments on Monday.

Berman's office last summer obtained an indictment against Epstein charging the former friend of Presidents Donald Trump and Bill Clinton with child sex trafficking.

Epstein, 66, was accused of sexually abusing dozens of underage girls in New York and in Palm Beach, Florida, from 2002 through 2005.

After Epstein died, Berman said the investigation into other people who may have abetted Epstein's crimes would continue.

But no one else has been charged.

Months after Epstein's death, Andrew sparked a furor with a disastrous interview with the BBC about his relationship with Epstein.

Andrew, among other things, denied having sex years ago with one of Epstein's accusers, Virginia Giuffre, as she has claimed. He said he was as incapable of sweating, as Giuffre described him doing when they were dancing at a London nightclub.