Sen. Richard C. Shelby (R-Ala.) said Monday that President Trump opposes the early release next month of John Walker Lindh, the American man who pleaded guilty in 2002 to fighting for the Taliban and was sentenced to 20 years in prison.

The news comes amid an outcry from members of the family of CIA officer Johnny “Mike” Spann, who have argued that Lindh played a role in Spann’s death in Afghanistan in November 2001. Spann’s relatives are Alabama residents.

In a tweet, Shelby said that he spoke with Trump on Monday night and that the president “stated that he supports my call for Lindh to serve his full sentence.”

“Lindh’s activities are deserving of a strong and strict punishment. Thank you, Mr. President,” Shelby said in the tweet.

According to the Federal Bureau of Prisons website, Lindh is currently an inmate at the Terre Haute Federal Correctional Institution in Indiana, with a release date of May 23, 2019.

Details on the reason for his early release were not immediately available. Credits for good behavior can reduce an inmate’s sentence by up to 15 percent, which would amount to three years in Lindh’s case.

The White House did not respond to requests for comment Monday night.

Lindh, who grew up in Maryland and California, was 20 years old when he joined a Taliban unit in Afghanistan in 2001. He was later captured, returned to the United States and eventually struck a plea deal with federal prosecutors that spared him a life sentence in the case.

Spann was the first American killed in Afghanistan. He was fatally shot during a prison uprising in Mazar-e Sharif that took place the same day he was questioning Lindh.

At the time of Lindh’s sentencing, some of Spann’s family members voiced displeasure with the agreement, which they said was unfairly lenient. They have spoken out in recent weeks in opposition to Lindh’s early release, and Shelby sent a letter to Trump last week stating that members of Spann’s family in Alabama had been in touch with him to voice their concerns.

“Mr. Lindh admitted to supporting the Taliban in Afghanistan and pled guilty to those accusations in July 2002,” Shelby wrote to Trump in the letter. “I believe that a 20-year sentence is a small price to pay for his participation in terrorist activities against his own country.”

He added that according to the National Counterterrorism Center, Lindh had “continued to advocate for global jihad and to write and translate violent extremist texts” as recently as 2016.

Foreign Policy magazine appears to have first reported on the National Counterterrorism Center document in 2017. The report also states that Lindh obtained Irish citizenship in 2013.

Shelby’s office confirmed Monday night that the senator and Trump had a phone conversation in which the president “informed Senator Shelby that he has his support in regard to calling for Lindh to serve his full sentence — 20 years.” It was unclear whether Trump plans to take any action.

Tom Jackman contributed to this report.