Alexandria, Virginia (CNN) -- An American-born man accused of posting an online attack against the creators of the animated TV series "South Park" due to a depiction of the Prophet Mohammed agreed to plead guilty Wednesday to providing material support to terrorists and other charges.
Under the agreement announced in federal court, Zachary Chesser, 20, also pleaded guilty to charges of communicating threats and soliciting crimes of violence.
The three charges carry a total maximum prison sentence of 30 years, and U.S. District Judge Liam O'Grady told Wednesday's court hearing that Chesser's defense agreed to a sentence of at least 20 years for acts "intended to promote a federal crime of terrorism."
O'Grady accepted the plea agreement and declared Chesser guilty as charged, setting the sentencing for February 25, 2011.
Chesser, dressed in a green prison jumpsuit with the word "prisoner" stenciled on the back, answered questions from the judge but made no statement. His once-long hair had been cut short.
Michael Nachmanoff, Chesser's federal public defender, said the case was different from other recent terrorism cases.
"Mr. Chesser has renounced violent jihad," Nachmanoff said. "He has accepted responsibility and is deeply remorseful. He is a young man who has taken the first steps towards putting his life back together. You saw one of those first steps today."
As part of the plea agreement, federal authorities agreed not to seek charges of aiding and abetting against Chesser's wife - Proscovia Kampire Nzabanita. She already is charged with making a false statement, which carries a sentence of up to five years in prison upon conviction. The couple has an infant son.
During the half-hour hearing, Chesser's defense said federal prosecutors agreed not to request that Chesser serve his time in the federal "supermax" prison in Colorado.
Chesser, a convert to Islam, is accused of posting an online attack against the creators of the animated TV series "South Park," as well as information on explosives meant to be used to kill civilians.
Prosecutors also say Chesser, of Fairfax County, Virginia, had exchanged e-mails with Yemeni-American cleric Anwar al-Awlaki, whose name has been linked to an attack and an attempted attack on the United States.
Chesser was questioned in 2009 about his internet postings and e-mail communications with al-Awlaki.
U.S. officials revealed that they had been staging court-ordered electronic surveillance of Chesser.
In April, Chesser, who also goes by the name Abu Talhah al Amrikee, authored a post on a radical Islamic website that included a warning to the creators of "South Park" after an episode of the cartoon series depicted the Prophet Mohammed in a bear suit.
The posting on Revolutionmuslim.com says: "We have to warn Matt [Stone] and Trey [Parker] that what they are doing is stupid and they will probably wind up like Theo van Gogh for airing this show. This is not a threat, but a warning of the reality of what will likely happen to them."
Van Gogh, a Dutch filmmaker, was murdered by an Islamic extremist in 2004 after making a short documentary on violence against women in some Islamic societies. The internet posting features a graphic photograph of van Gogh with his throat cut and a dagger in his chest.
The entry goes on to advise readers: "You can contact them [the makers of "South Park"], or pay Comedy Central or their own company a visit at these addresses ... " and lists Comedy Central's New York address and the Los Angeles, California, address of Parker and Stone's production company.
Chesser told CNN at the time that providing the addresses was not intended as a threat but to give people the opportunity to protest.
An affidavit from prosecutors details other videos and postings from Chesser, including a link to an Army Ranger handbook with information on explosive devices and a post about "desensitizing" police by leaving fake suspicious bags around in public places.
An FBI agent who spoke with Chesser on July 14 said that "Chesser stated that he was an influential person in the Jihadi community, and could be considered one of the top individuals in this area."
Chesser tried to fly to Uganda on July 10 and then on to Somalia.
According to an affidavit, he tried to take his infant son with him, telling his wife it was part of his "cover" to make it less likely anyone would suspect he was trying to go to Somalia to join the militant group Al-Shabaab.
The court documents said Chesser was not allowed to depart the country July 10 but was told by the airline he was on the "no-fly list" and was questioned by a Secret Service agent. He was not arrested, and according to the documents, he contacted an FBI agent and said he wanted to provide information about Al-Shabaab.
In subsequent interviews with the FBI, Chesser allegedly said he had been in contact with Al-Shabaab, felt that he would have no problem joining the group when he reached Somalia and knew it had been designated as a terrorist group by the U.S. government.
Court documents say Chesser thought that after training, he would be placed in the group's media branch but that people in that position still engage in fighting.
Chesser was arrested on July 21. A search of Chesser's home uncovered a handwritten note called "How to Destroy the West" that contained a bulleted list of activities.
"Under the attacks on personnel," the affidavit said, Chesser wrote "put out a message to the Muslims to go buy guns and kill soldiers" and "Fill a tanker with explosives and Ricin," a toxic protein extracted from castor beans.
CNN's Tom Cohen and William Mears contributed to this story.