Authorities in the US have formally requested Prince Andrew aid them in a criminal probe into sex offender Jeffrey Epstein, according to reports.
A mutual legal aid assistance (MLA) has been submitted to the UK Home Office by the American Department of Justice, requesting that Prince Andrew answer questions as a witness in the probe.
The request comes as federal prosecutors in the US investigate Epstein's offending, and in the wake of a new Netflix documentary on the disgraced financier.
The documentary features Virginia Giuffre, also known as Virginia Roberts, who has claimed that she was trafficked to the UK by Epstein and subsequently had sex with the Duke of York in 2001.
The duke has refuted the claim, denying he had any form of relationship or sexual contact with Ms Giuffre.
Ms Giuffre has urged the duke to speak with authorities, but a US lawyer said in March that the prince had "completely shut the door" on co-operating with investigators over the probe.
Following a disastrous Newsnight interview in November about his relationship with Epstein, Andrew stepped down from royal duties.
In the days following the interview last year, the duke said in a statement that he would be "willing to help any appropriate law enforcement agency with their investigations, if required".
However, Geoffrey Berman, who is leading the Epstein inquiry, told reporters in March that the duke has in fact been uncooperative with regards to the investigation:
"Contrary to Prince Andrew's very public offer to co-operate 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 co-operation and our office is considering its options."
Ms Giuffre alleges the duke had sex with her three separate times, including when she was 17 - still a minor under US law.
In an interview with BBC Panorama, Ms Giuffre said that she was left "horrified and ashamed" after an alleged sexual encounter with Andrew in London in 2001.
MLA requests by other states are used to obtain assistance in a prosecution or investigation of criminal offences, usually when cooperation can't be obtained by law enforcement agencies.
According to Home Office guidance, it is "usual policy" that the existence of a request is neither confirmed or denied.