(CNN) A federal judge on Friday ordered George Aref Nader to stay in jail until his trial for transporting child pornography, citing the danger the former witness to Robert Mueller's probe poses to the community.

Nader, 60, was once an informal adviser to the Trump White House and has attended high-level meetings with members of President Donald Trump's inner circle. He was also a key cooperator in Mueller's investigation. Now he'll live in an Alexandria, Virginia, jail awaiting trial on a federal charge transporting sexually explicit videos of underage boys.

Prosecutors said Nader posed an "extreme danger to the community" and federal Magistrate Judge Ivan Davis agreed. The judge cited Nader's decades-old convictions in the US for possessing child pornography and for "hands-on contact with minors" in the Czech Republic.

"Forty years ago, he had a propensity, and 40 years later he still has it," Davis said of Nader's repeated contact with minors. "That's a problem. ... He has not gotten any better, it appears."

During a contentious hearing, Nader's defense attorneys unsuccessfully pleaded with the judge to release him from jail, so he could move to a long-term medical facility. Nader recently had open-heart surgery and is dealing with a "very serious health condition," his lawyers said.

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