Fort Bragg, N.C. — A soldier pleaded guilty Thursday during a court-martial to knowingly infecting a 17-year-old boy with HIV.

Pfc. Johnny Lamar Dalton, 25, a member of the 82nd Airborne Division, pleaded guilty to three counts of aggravated assault by means likely to cause grievous bodily harm or death and one count each of committing an indecent act, violating an order from an Army officer to inform sexual partners of his HIV and using marijuana.

Military judge Col. Patrick Parrish sentenced Dalton to 40 months in military prison, a reduction in rank to private and a dishonorable discharge. The prosecution had requested six years in confinement in addition to the discharge.

Dalton broke down in tears during the hearing, apologizing to his wife and his 4-year-old daughter for his actions.

"Of everyone I let down, I let her down the most," he said of his daughter. "I would just like to tell her I'm sorry."

Dalton joined the Army three years ago and learned he was infected with HIV in June 2006. His illness barred him from deploying, but he was able to stay in the Army as long as he could perform his job.

Last November, he was ordered not to have sex without first telling his wife or other potential partners of his HIV infection, and he signed an order to that effect, authorities said.

The mother of the unidentified boy, who is now 18, said her son first met Dalton in a gay online chatroom and then in person.

Doctors conducting routine blood tests in February found that the teen was HIV-positive.

"When someone basically shortens your life, whether it's your's or your child's, you feel cheated," the teen's mother said in July.

Dalton was arrested in July after a five-month investigation by Fort Bragg military police and the Cumberland County Sheriff's Office. He has been confined at Camp Lejeune since his arrest.

"We were caught up in the moment," Dalton told Parrish in trying to explain his actions with the teen.

Tarika Dalton testified that she would stand by her husband.

"My husband is not a bad person and is definitely sorry for what he's done," she said.

Spc. Camilla Milhorn, who has worked with Johnny Dalton at Fort Bragg, also testified in his defense.

"He's a great person who just made a bad mistake," Milhorn said.

The teen's mother said she would have preferred a longer sentence, but was glad the case had been resolved.

"I feel for his daughter. She's without a father now," she said.