A deranged man who confessed to stabbing a 10-month-old baby in her stroller last month told cops: "I had to kill something."

Laura Italiano:

"I'm sorry now that I did that," the knife-swinging maniac admitted on the night cops say he nearly disemboweled tiny Isabelle Avins — who miraculously survived — as her nanny pushed her in Washington Heights.

"I'll never do it again," he promised, according to police statements released yesterday. "But at the time, I had to do that to feel better."

The chilling statements were released as Bernard Derr, 48, pleaded not guilty in Manhattan Supreme Court to charges of attempted murder and assault.

Justice Charles Solomon ordered that the gray-bearded, disheveled man be examined by two court-appointed psychiatrists to see if he is fit to stand trial.

Meanwhile, the baby is beginning her fourth week in a hospital bed. She has had multiple surgeries at Columbia Presbyterian Hospital to repair serious internal injuries from a single slicing stab wound.

"The baby is progressing well, given the circumstances," said a law enforcement source.

In talking to police the night of the attack, Derr — a mental patient who takes multiple anti-psychotics — brushed off his alleged brutality, describing it as the logical response to having fought with his two roommates in their Fort Washington Avenue group home.

"Lately, they been getting on my nerves," he said of "Oassie" and "Billy." "They'd been hounding me to clean up, do the dishes, stuff like that.

"Those two fellas made me angry. I was going to stab them and then decided to stab a baby.

"I knew it was wrong to stab the baby, but I had to feel better," he explained.

Cops say that after the stabbing, Derr left the screaming, gasping baby and her hysterical nanny, and walked quietly to his apartment nearby.

"After I stabbed the baby, I was calm and felt tired. I calmed down and waited for the police.

"I knew they would [come] because I killed the baby," he concluded.

Man Accused Of Stabbing Baby To 'Feel Better'

Suspect tells cops stabbing baby made him feel better