ATLANTA — A Georgia man was arrested on Wednesday on suspicion of planning to attack the White House with explosives and other weapons, federal prosecutors said.

Investigators monitored the man for months, and then arrested him when he tried to buy weapons from an undercover F.B.I. employee posing as a dealer, according to an F.B.I. affidavit.

The suspect, identified as Hasher Jallal Taheb, 21, of Cumming, Ga., had also discussed attacking other buildings in the Washington area, and at one point said he wanted to attack the Statue of Liberty, according to the affidavit. Officials said on Wednesday that the suspect was believed to have acted alone.

“All potential threats have been neutralized, and they have been under control from the inception of this case,” Byung J. Pak, the United States attorney for the Northern District of Georgia, said at a brief news conference in downtown Atlanta announcing the arrest.