A US man has been charged with assault after he allegedly broke wind on a police officer.

Police say they were fingerprinting Jose Cruz, 34, when he moved near Patrolman T.E. Parsons, lifted his leg and passed gas "loudly" on the officer.

Cruz then allegedly waved the air in the direction of Parsons, who was preparing a breath test machine at South Charleston police HQ, West Virginia.

"The gas was very odorous and created contact of an insulting or provoking nature with Patrolman Parsons," the complaint says.

Cruz, of Clarksburg, had just been arrested under suspicion of drink driving after police saw him driving without headlights, reports the Charleston Daily Mail.

Officers said he was unsteady on his feet and smelled of alcohol when they pulled him over.

Cruz was charged with drink driving, assaulting a police officer and obstruction.