A detective testified yesterday he felt uneasy from the start of an undercover operation that resulted in the shooting death of an unarmed bridegroom outside a strip club on his wedding day.

“I felt uncomfortable,” Detective Hispolito “Hip” Sanchez said, suggesting police were unprepared for an unfamiliar and hostile setting inside the Kalua Cabaret in Queens on November 25, 2006. “I just didn’t feel good about it,” he said.

Prosecutors at the trial of three officers charged in the killing of Sean Bell have argued that an undercover operation targeting prostitution was doomed by a shoot-first-and-ask-questions-later mentality. But Detective Sanchez’s first public account of the incident also appeared to support defense claims the five New York City Police Department shooters had reason to believe trouble was brewing at closing time.

Detective Sanchez, 34, said that after mixing with the crowd for four hours and downing two beers to keep his cover, he witnessed a crude exchange at 4 a.m. outside the club between members of Bell’s party and a woman, who told the four men, “I’m not (having sex) with all y’all.” He said there was a simultaneous stare-down between the bridegroom and another patron dressed in black and acting as though he had a gun. The officer claimed to have overheard Bell say, “Let’s f— him up,” and a friend, Joseph Guzman, twice blurt out, “Yo, go get my gun.”