A key witness in special counsel Robert Mueller’s Russia investigation has been charged with child sex trafficking “with intent to engage in criminal sexual activity” and transporting child pornography.

An unsealed federal indictment in the Eastern District of Virginia reveals George Aref Nader allegedly transported a 14-year-old boy from Europe to the United States in 2000 to solicit the teenager for prostitution.

According to the indictment, Nader engaged in sexual acts with the boy in his Washington, DC home.

The Lebanese-American businessman  was also charged under seal with two counts of transporting “obscene materials” and “visual depictions of minors engaged in sexually explicit conduct.”

He was apprehended by law enforcement in June immediately upon his arrival at John F. Kennedy International Airport in New York.

Following his arrest, a federal judge rejected a request from his attorneys to allow him to seek recovery from recent open-heart surgery at a long term medical facility and ordered him to remain in a Virginia jail until the completion of his trial.

In federal court in Friday, Nadler plead not guilty to the charges and is slated for a court appearance September 30. He was previously convicted of a federal child-pornography charge in Virginia in 1991 and plead guilty to sexual contact with children in the Czech Republic. If convicted on the new charges, he faces a mandatory minimum of 15 years in prison and a maximum of 40 years.

Nadler brought an IPhone into the United States containing dozens of sexually explicit videos featuring underage boys, some as young as 2 years old, federal prosecutors allege. Court records show the pornographic footage was discovered by FBI agents working for Mueller when his electronic devices were examined at an airport.

Nader, who served as an adviser to Saudi Arabia and the United Arab Emirates, was a key cooperator in Mueller’s probe of foreign influence in the 2016 election. His name is referenced more than 100 times in Mueller’s report which details his work arranging a January 2017 meeting in the Seychelles between Trump associate Erik Prince and Kirill Dmitriev, a Russian businessman with close ties to President Vladimir Putin.

Mueller’s team last year was reportedly investigating whether the UAE sought help from Nader to gain political influence by putting money into Trump’s 2016 campaign.

He met several times with individuals associated with the Trump campaign throughout the election and into the early days of the administration, met he reportedly met with Trump’s son-in-law and senior White House adviser Jared Kushner, former chief strategist Steve Bannon and former national security adviser Michael Flynn.