Boston, Massachusetts - Jack Teixeira, the US airman accused of leaking top-secret Pentagon documents in an online chat forum, will plead guilty to charges that could land him in prison for decades, court documents showed Thursday.

Prosecutors requested a change of plea hearing for March 4, at which Teixeira will confirm his decision to reverse his current plea of not guilty.

The Massachusetts Air National Guard IT specialist was arrested in April for allegedly orchestrating the most damaging leak of US classified documents in a decade, some of which concerned the war in Ukraine.

He is facing six counts of retaining and transmitting national defense information. They each carry sentences of up to 10 years in prison.

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Teixeira is accused of posting the documents – some dated as recently as early March 2023 – to a private chat group on the social media platform Discord.

Some of the files later appeared on other sites, including Twitter, 4Chan, and Telegram.

The documents, which soon spread across the internet, pointed to US concern over Ukraine's military capacity against invading Russian forces and showed Washington had apparently spied on allies Israel and South Korea, among other sensitive details.

It was the biggest such breach since the 2013 dump of National Security Agency documents by Edward Snowden and raised tough questions about access by Teixeira and other junior staffers to high-level secrets.

Teixeira was an airman first class, the third-lowest rank for enlisted US Air Force personnel and had possessed a top secret security clearance since 2021.

In May 2023, a judge ordered that Teixeira remain in jail after prosecutors argued he posed an ongoing risk to American national security.

Prosecutors said that Teixeira might still have access to classified documents and that "hostile" nations could aid his escape if he was released from prison.

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They also cited his history of making "violent" statements.

Teixeira wrote on social media in November 2022 that he wanted to "kill a ton of people" because it would be "culling the weak minded," the prosecution wrote in a court document.

Teixeira was detained in April 2023 in a dramatic arrest broadcast live on TV networks.