After the Washington Post first identified Schulte on Tuesday, his lawyer released a statement to say he is "deeply saddened" that he may face espionage charges.

Schulte, 29, already held without bail in Manhattan on child pornography charges, learned last Friday during a New York court appearance that additional charges were likely to be filed against him in about 45 days from what Assistant US Attorney Matthew Laroche said was a "broader investigation" unrelated to the pornography case.

"Mr Schulte has spent years working to ensure the safety of his country and is deeply saddened to hear that he could face charges of espionage," assistant federal defender Sabrina Shroff said on Tuesday.

At a January hearing, Laroche said Schulte was a target of an ongoing investigation into the theft of tools that were used by the CIA to spy overseas. His defence lawyers have insisted he was not involved.

The US government has all but publicly acknowledged the embarrassing leak from the CIA's Centre for Cyber Intelligence. President Donald Trump told a television host then, "I just want people to know the CIA was hacked, and a lot of things taken".

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At January's hearing, Laroche said the material was taken from the CIA during the more than six years that Schulte worked for the agency in various positions, including technical development officer.

"The government immediately had enough evidence to establish that he was a target of that investigation," Laroche said. "They conducted a number of search warrants on the defendant's residence."

Laroche said he disagreed with Schulte's lawyer at the time, who claimed the search warrants had not yielded anything consistent with the material released by WikiLeaks. "In fact, our investigation is ongoing," Laroche said. "He remains a target of that investigation."

Last Friday, Laroche told US District Judge Paul A. Crotty that the new charges were unlikely for several weeks.

"We're consulting with a lot of folks that are not within our office, so we're moving as quickly as we can on that front," he said.

The cryptic description at Friday's hearing led Shroff, who entered the case in March, to demand more.

"Are they secret charges that I'm not allowed to know about? What are these charges?" Shroff asked, saying she wanted to know of possible charges, whether they be sedition or something else. "Are they charging him with espionage?"

Laroche said it involved an ongoing grand jury investigation and added, "I don't think we have an obligation to disclose it at this time, but we certainly have had discussions with Ms. Shroff about the nature of the underlying investigation".

Schulte, of New York, is being held at the Metropolitan Correctional Centre in Manhattan.

Jacob Kaplan, Schulte's attorney at the January hearing, told the court that "the government had full access to his computers and his phone, and they found the child pornography in this case, but what they didn't find was any connection to the WikiLeaks investigation".

Washington Post, AP