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A Georgia man accused of plotting to attack the White House and other landmarks pleaded guilty Wednesday, according to federal prosecutors and court documents.

Hasher Jallal Taheb, 23, had been the subject of an undercover investigation that lasted for more than a year and was arrested in January 2019 as he arrived to pick up what he expected to be semi-automatic rifles, explosives and an anti-tank weapon, authorities said.

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He pleaded guilty to attempting to destroy, by fire or an explosive, a building owned by or leased to the United States, the U.S. Attorney's Office for the Northern District of Georgia said in a statement.

Taheb was arrested after he met with undercover agents at a Buford, Georgia, parking lot where the deal for the weapons was supposed to occur, according to a criminal complaint. The rifles, the explosives and the anti-armor weapon, an AT-4, were all inert.

As part of a plea agreement, prosecutors agreed to recommend a sentence of 15 years, according to court documents. Sentencing is scheduled for June 23.

Taheb wanted to attack the White House and the Statue of Liberty, but later broadened the targets to include the Washington Monument and Lincoln Memorial and a synagogue, prosecutors said.

Investigators believe Taheb was working on his own, an FBI official said at the time of his arrest.

The investigation began after a community member sent in a tip in March 2018 that Taheb had become "radicalized" and made plans to travel abroad, according to the complaint. When he was unable to travel abroad because of passport issues, he allegedly began planning an attack in the U.S.

An e-mailed request for comment from a federal public defender listed as representing Taheb was not immediately returned early Thursday.