George Nader, a key witness in the special-counsel probe of Russian interference in the 2016 presidential election, was sentenced Friday to 10 years in prison and a lifetime of supervised release for transporting a child into the country for sex and possessing child pornography.

“I take great pride in my professional life and the work I have done for the United States,” Nader, 61, said in Alexandria, Va., federal court Friday. “I am sincerely, deeply sorry for the pain and suffering I have caused.”

Nader also agreed to pay $150,000 in restitution to the victim, who was 14 at the time Nader brought him from the Czech Republic to the United States.

He still faces charges in D.C. federal court of helping to funnel illegal foreign contributions to both the Hillary Clinton campaign and Donald Trump’s inaugural fund.

A Lebanese American businessman, Nader for decades has wielded significant influence in negotiating peace treaties and financial agreements between the United States and countries in the Middle East.

“He’s lived most of his life in international privilege and to much acclaim. He’s worked with presidents and princes, the powerful and the infamous,” Assistant U.S. Attorney Jay Prabhu said at sentencing. “But that wasn’t Mr. Nader’s only passion. . . . Mr. Nader has had a sexual interest in minors for over 35 years.”

Nader became entangled in special counsel Robert S. Mueller III’s investigation because he helped set up a January 2017 meeting between Trump associate Erik Prince and a Russian official.

During that investigation, FBI agents searched Nader’s phones and found what appeared to be child pornography in WhatsApp messages sent to him. Nader maintains that while the images showed naked children, they were meant to be humorous rather than sexual and he did not realize they were on his phone. But he admitted to receiving an email containing child pornography in 2012 and bringing a child into the country for sexual purposes in 2000.

“It has been a long journey and it still will be,” the victim, now 35, said in a statement written in Czech and translated in court. “I hated myself and was ashamed of myself.” He said seeing Nader prosecuted was helpful in “restoring my soul and my health.”

Defense attorney Jonathan Jeffress said that in recent years, Nader has learned to control his urges “as he has aged and as he has realized that his work doing good things for people, doing good things for peace, doing good things for the United States became more important to him.”

Prosecutors had agreed to ask only for the mandatory minimum sentence of 10 years.

Nader had been investigated and convicted of similar conduct in the past, but he has never been punished so severely. In 1991, after being convicted of transporting child pornography in Alexandria, he was given a six-month sentence in part because he was actively involved in negotiating the release of hostages from Lebanon. In 2003, he was sentenced to a year in prison in the Czech Republic for soliciting underage boys.

Throughout the years, he has been involved in high-level diplomatic negotiations in Israel, Syria, Saudi Arabia and Iraq. He helped arrange Trump’s first trip to Riyadh, the Saudi capital.

“Nader has conducted countless international missions and helped facilitate the strong allegiance between the United States and countries of that region,” his attorneys wrote. “Nader sincerely hopes that, after the period of incarceration to be imposed in this case, he will be able to resume his efforts working toward peace in the Middle East.”