Two months ago, Britain’s Prince Andrew issued a public statement saying he would be willing to help American law enforcement officials with their investigation into allegations of sex-trafficking by Jeffrey Epstein and his associates.

F.B.I. agents and federal prosecutors in New York took him at his word. They reached out to his lawyers and asked to interview him.

There was no response at all, according to three people familiar with the investigation.

On Monday, in a rare move, the United States attorney in Manhattan publicly called out the prince for breaking his commitment.

“To date, Prince Andrew has provided zero cooperation,” the prosecutor, Geoffrey S. Berman, said in response to a question at a news conference outside Mr. Epstein’s Upper East Side mansion.