(Adds details, background)
WASHINGTON, May 7 (Reuters) - An Ohio man already in custody for an alleged plot to attack the U.S. Capitol in January has been charged with the additional crime of attempting to provide material support to the Islamic State militant group, the U.S. Justice Department said on Thursday.
Christopher Lee Cornell, 21, pleaded not guilty in federal court in Cincinnati in January to plotting an attack on the U.S. Capitol with guns and bombs. He is being held without bail pending trial.
He allegedly researched the construction of pipe bombs, purchased a semi-automatic rifle and 600 rounds of ammunition and made plans to travel to Washington to carry out the plot, according to the original indictment.
The other charges he already faces are attempted murder of government officials, possession of a firearm to commit a crime and solicitation to commit a violent crime.
In March, prosecutors asked a judge to limit Cornell's phone access in jail after he gave an interview to Cincinnati's FOX 19 WXIX TV in which he said that he wanted to shoot President Barack Obama in the head.
A lawyer for Cornell was not immediately identifiable.
The additional charge was brought by a federal grand jury in Cincinnati and carries a sentence of up to 15 years in prison.
Cornell faces up to 45 years behind bars for the other charges.
(Reporting by Lindsay Dunsmuir; Editing by Emily Stephenson and Leslie Adler)