Harlem Suarez, 23, from Key West, Florida and a son of Cuban immigrants, is seeking a jury trial, his lawyer Richard Della Fera told reporters after the hearing in federal court.
Suarez was arrested in July after acquiring material to make a backpack bomb he planned to detonate on a beach in Key West, according to court documents.
Suarez is charged with "knowingly attempting to use a weapon of mass destruction against a person or property within the United States."
Della Fera said he would seek a psychiatric evaluation of Suarez, whom he described as naive and "foolish.
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Relatives and friends of the defendants have described him as impressionable and inclined to believe everything he reads on the Internet.
Suarez faces life in prison if convicted.
Dozens of people have been arrested in recent months in the United States for trying to abet or join the Islamic State group, a jihadist organization which controls broad stretches of territory in Iraq and Syria.