Washington (CNN) The father of a former CIA officer killed in Afghanistan in 2001 has formally petitioned for an investigation of extremist comments allegedly made in prison by American Taliban fighter John Walker Lindh, who is scheduled to be released later this week.

In a letter to a Virginia federal court, Johnny Spann said Lindh reportedly "ignored" conditions placed on him in a plea agreement he reached in 2002.

Mike Spann was killed in an uprising of Taliban prisoners in 2001 at a detention facility in Afghanistan where Lindh was being held. After charges that touched off a debate in the early days of the war on terror, Lindh, who was dubbed the "American Taliban," pleaded guilty in 2002 to aiding the Taliban.

He is due to be released from prison this week after serving 17 years of a 20-year sentence.

Spann has protested the early release of Lindh and taken the issue up with lawmakers, including Sen. Richard Shelby, an Alabama Republican, who said last month that he raised the issue with President Donald Trump, who agreed that Lindh should serve his full sentence.

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