An on-duty World Trade Center guard got into a fight over french fries at a nearby McDonald’s early Monday morning — and ended up stabbing a man, police said on Monday.

Saul Puente, 54, who works for AlliedBarton Security Services, became furious when Michael Ruet, 20, threw fries at him around 3:40 a.m. inside the Broadway eatery, police said.

They took the argument outside, where Puente pulled a knife, according to cops.

The guard allegedly slashed Ruet in the face and stabbed him in the chest before fleeing down Fulton Street.
Cops busted Puente a few blocks away.

Ruet was taken to Bellevue Hospital in stable condition, and the guard was treated for a laceration to the lip at New York-Presbyterian Lower Manhattan Hospital.

Puente has been charged with felony assault, according to police.

AlliedBarton Security said it was conducting an investigation into what happened.