WASHINGTON, Sept 24 (Reuters) - An Illinois man has been arrested for attempting to detonate a vehicle bomb outside a federal building in the state capital, the Justice Department said on Thursday, a case unrelated to the New York terrorism plot.

Michael Finton, also known as Talib Islam, was arrested in Springfield, Illinois, and charged with attempted murder of federal officers or employees and trying to use a weapon of mass destruction, charges that carry a life sentence.

“Fortunately, a coordinated undercover law enforcement effort was able to thwart his efforts and ensure no one was harmed,” Assistant Attorney General for National Security David Kris said in a statement.

The criminal complaint said Finton converted to Islam while in prison on other charges. It said he idolized an American who allied with the Taliban, John Walker Lindh, drawing the attention of law enforcement authorities.

After returning from a trip to Saudi Arabia in 2008, Finton met and told an individual, who turned out to be a law enforcement source, that he wanted to fight against Israelis in the Gaza Strip, according to the complaint.

In early 2009, “it appeared that Finton was on the verge of taking action, so it was decided to proactively provide him with an opportunity for action that we controlled, rather than merely hoping to be able to find out and stop him,” according to a government affidavit.

He was eventually introduced to an undercover FBI agent who began working with him to plot an attack, but Finton was repeatedly told he could walk away at any time, according to the Justice Department.

Eventually, Finton picked the federal building in Springfield as the target and on Wednesday he parked a van he believed carried one ton of explosives at the location, the complaint said.

Finton walked away and tried to detonate the bomb with a cell phone call, but instead of setting it off, he was arrested.

The Justice Department said the case was unrelated to another suspected terrorism plot in New York where an Afghan-born man was charged with conspiring to launch a bombing attack in the United States using chemicals that form triacetone triperoxide. (Reporting by Jeremy Pelofsky, editing by Jackie Frank)