He was arrested during an undercover law enforcement operation while trying to obtain explosives and guns, the Justice Department said in a statement.
Ulugbek Kodirov, 22, pleaded guilty in a court in Birmingham, Alabama to one count of providing material support to terrorist activity, one count of threatening to kill the president and one count of possession of a firearm by an illegal alien.
As part of his plea agreement with prosecutors, Kodirov admitted he had communicated with a suspected member of the Islamic Movement of Uzbekistan identified only as "the Emir" who suggested that he kill Obama.
His meetings with the Emir led him to seek out a way to obtain explosives and weapons, the plea agreement says.
The US State Department lists the Islamic Movement of Uzbekistan as a foreign terrorist organization.
Kodirov also admitted to discussing with another person his desire to kill Obama and ways to carry out the assassination.
The other person -- who was not identified by the Justice Department -- introduced Kodirov to an undercover law enforcement agent from whom the Uzbek man planned to purchase weapons.
They met July 13, 2011 at a motel in Leeds, Alabama. The agent showed Kodirov an M15-A1 machine gun, a sniper rifle with a telescopic lens and four disassembled hand grenades, the statement said.
Kodirov chose the machine gun and hand grenades then tried to leave. He was arrested before he departed from the motel.
Kodirov had entered the United States from Uzbekistan on a student visa in June 2009. His visa was revoked on April 1, 2010 after he failed to enroll in school.
However, he did not leave the United States. He was living in an extended-stay motel in Pelham, Alabama, when he was arrested.
Kodirov faces up to 30 years in prison on the charges.
"I also want to express my appreciation to the Muslim community of Birmingham, which was instrumental in helping law enforcement shut down this threat," said US Attorney Joyce White Vance.