A California man who was captured fighting for the Taliban in Afghanistan in November 2001 has been released from prison.
The federal Bureau of Prisons said that John Walker Lindh, known as the American Taliban, was released on May 23 from a high-security prison in Indiana.
Lindh, 38, was set to be freed three years early for good behavior in a 20-year sentence.
His early release sparked criticism, amid concerns that he may still harbor extremist views.
"There is something deeply troubling and wrong about this," Secretary of State Mike Pompeo said on Fox News.
President Donald Trump told reporters the authorities will be closely watching Lindh, adding that nothing could be done to prevent his release.
Lindh converted to Islam at 16 and joined the Taliban in mid-2001. After the United States invaded Afghanistan following the September 11, 2001, attacks, he was one of hundreds of Taliban fighters captured on November 25, 2001.
On the eve of Lindh's release, U.S. television station KNBC said it had received letters from him during his imprisonment in which he allegedly praised the Islamic State extremist group and called himself a political prisoner.
It was unclear why the letters, dating back to 2014-15, only came to light now.
Lindh, who gained Irish citizenship while in prison, cannot obtain a passport or travel abroad.
His lawyer Bill Cummings told CNN Lindh will now move to Virginia and live under the direction of his probation officer.
Lindh's release underscores the fact that, almost two decades later, the U.S. war against the Taliban continues.
Veteran U.S. diplomat Zalmay Khalilzad has been conducting several rounds of peace talks with the militants.
But the Taliban refuses to speak to the government in Kabul and has not renounced violence.
Khalilzad on May 22 briefed U.S. lawmakers in Washington on the progress of the talks.
The meeting was classified, but media reports suggested that the results of Khalilzad's efforts were met with skepticism on Capitol Hill.
