A convicted counterfeiter with an apparent grudge against the courts was arrested Thursday on charges of plotting to blow up a federal courthouse, although he never had materials to make a truck bomb, authorities said.

Prosecutors said Gale William Nettles, 66, was arrested with a pickup truck containing 1,500 pounds of fertilizer that he allegedly thought was volatile ammonium nitrate, the farm chemical used to blow up the Oklahoma City federal building in 1995, killing 168 people.

Nettles had planned to sell the chemical to terrorists who would blow up the Dirksen Federal Building in downtown Chicago, U.S. Attorney Patrick J. Fitzgerald said in announcing the charges. But the other people involved, including the "terrorists" and the people who sold him the fertilizer, were cooperating witnesses or federal agents, Fitzgerald said.

Nettles told the undercover agent he could make a 3,000-pound fertilizer bomb.

"He had a rational plan to build a bomb. We weren't going to wait to see if it would work," Fitzgerald said.

Nettles was arrested at a park early Thursday with the pickup truck when he met the undercover agents who he thought were terrorists, according to the criminal complaint. The fertilizer he obtained in the sting does not have the explosive potential of ammonium nitrate.

A federal magistrate ordered Thursday that Nettles be held until a detention hearing Tuesday. No plea was entered, and defense attorney John Theis declined to comment afterward.

Fitzgerald said Nettles was not working with any other groups but had asked cooperating witnesses about contacting al Qaeda and the Islamic Resistance Movement, known as Hamas.

Thomas Kneir of the FBI discusses the arrest with U.S. Attorney Patrick J. Fitzgerald, center, and James Tantillo of the U.S. Marshals Service.