By Joseph Ax

NEW YORK (Reuters) -- A New York teenager charged with conspiring to support Islamic State group should be tried as an adult, despite having been only 17 at the time he allegedly committed the crime, a federal judge ruled.

The teenager, who remains unidentified in court papers, is among a half dozen men in New York and New Jersey whom authorities have arrested since June as part of a broader investigation into a purported conspiracy to aid the militant group.

U.S. authorities have pursued a number of “lone wolf” plotters who were apparently inspired by Islamic State’s propaganda, including investigations in all 50 states.

Islamic State, also known as ISIS or ISIL, claimed responsibility for last week’s attacks in Paris that killed 130 people. The group also claimed responsibility for downing a Russian airliner in Egypt last month, killing 224.

Federal authorities said the teenager, who is now 18, was friends with Munther Omar Saleh, a college student in the New York City borough of Queens.

Saleh and the unnamed man discussed plans to assemble an explosive device to set off in the New York metropolitan area, according to prosecutors. On June 19, federal agents were following the two men in a surveillance vehicle when the men got out of their car and ran at the agents, prompting their arrest at gunpoint.

The Justice Department had filed a sealed motion to try the teenager as an adult, citing the seriousness of the charged crime and the fact that he was just shy of 18 at the time of his arrest.

In an opinion made public this week, U.S. District Judge Margo Brodie in Brooklyn agreed with the government’s argument.

“Although their ultimate goals were never accomplished, this fact does not undermine the serious nature of their alleged conspiracy,” she wrote.

The teenager’s court-appointed lawyer declined to comment.

Two of the other men charged in the conspiracy, Samuel Topaz and Alaa Saadeh, have pleaded guilty in New Jersey. They admitted in court that they discussed plans to travel overseas to join Islamic State with Saleh and Saadeh’s brother, Nader Saadeh, who has also been charged.

Fareed Mumuni, a New York man, was arrested in June after authorities said he tried to stab a federal agent executing a search warrant at his home.

Mumuni had discussed attacking law enforcement with a bomb with Sadeh, according to prosecutors.

(Reporting by Joseph Ax; Editing by Tom Brown)