RICHMOND, Va. — An Army National Guard officer charged with driving an armored personnel carrier off base while under the influence of drugs insisted Thursday he was ordered to do so as part of a training exercise and called the charges against him "completely bogus."

But a spokesman for the Virginia National Guard denied 1st Lt. Joshua Yabut's claim.

"Lt. Yabut was not authorized by the brigade commander or anyone else to drive the armored personnel carrier off Fort Pickett to any location for any reason," spokesman A.A. "Cotton" Puryear wrote in an email.

Yabut told The Associated Press he was first notified of the training exercise by his commander a week before he drove the vehicle away Tuesday evening from Fort Pickett. Yabut said he was later given the command in coded military language to conduct the exercise, which he said was aimed at gauging police response.

"I didn't want to do it, but I believed it was a lawful order, and as a commissioned officer I was required to do so," Yabut said.

Yabut, 29, of Richmond, Virginia, was arrested in downtown Richmond following a two-hour police chase. He spoke to the AP by phone from a psychiatric hospital. He was taken there Wednesday after he was arraigned on charges of driving under the influence of drugs, unauthorized use of a National Guard vehicle and evading police.

Yabut said he was not under the influence of illegal drugs. He said the only drug he has taken recently is a low dose of Lexapro, which he said he was prescribed for anxiety after he returned in 2009 from a deployment in Afghanistan. He said the drug has never altered his behavior.

"I think the toxicology report will show that those charges are completely false, and I don't even know why I would be charged with that to begin with," he said.

A state trooper who is listed as the arresting officer wrote in court documents that Yabut had "glassy eyes" with dilated pupils, slurred speech and was "unsteady on his feet."

"Mr. Yabut had no idea where he was at that time," the trooper wrote. He also wrote that Yabut's dilated pupils "are indicative of opioid use."

Sgt. Keeli Hill, a Virginia State Police spokeswoman, said Thursday that she couldn't give specifics about what drugs Yabut might have used, saying an investigation was ongoing.

Yabut's lawyer did not respond to several phone messages and emails seeking comment.

The Guard said Yabut is assigned as the commander of the Petersburg-based Headquarters Company, 276th Engineer Battalion. He has more than 11 years of service, and was deployed to Afghanistan from 2008 to 2009 with the Illinois National Guard.

The armored personnel carrier, which drives on tracks like a tank, topped out at speeds of about 45 mph (70 kph) on its journey to the state capital. Police couldn't stop it, so they ended up escorting it, sirens blaring, before Yabut stopped and got out near City Hall.

Yabut said police shot him with a stun gun and set a dog on him before taking him into custody.

"I didn't just run in to an APC and drive it off," Yabut said. "It was prepped. It was prepared with 60 miles of fuel and soldiers assisted with the preparation."