Reputed Mafia boss John Gotti is a bully who ordered the shooting of a union leader to avenge the trashing of a mob-linked restaurant because "he couldn't allow a challenge to go unpunished," a prosecutor charged Saturday.

The remarks in state Supreme Court in Manhattan marked the beginning of the assault and conspiracy trial for Gotti, who prosecutors claim is "the head of the Gambino crime family," the nation's largest and most powerful mob organization."They rule by terror and intimidation," Assistant District Attorney Michael Cherkasky told the seven-woman, five-man jury.

He pointed at Gotti, who calmly gazed ahead from the defense table, wearing a black pin-striped double-breasted suit, red and black patterned tie and diamond pinky ring.

"He controls the Gambinos with an iron fist," said Cherkasky in his opening statement in the packed courtroom.

Gotti, 49, is charged with ordering the May 1986 shooting and wounding of John O'Connor, a carpenters union official.

His co-defendant, Anthony "Tony Lee" Guerrieri, 60, a reputed Gambino soldier, is accused of helping plan the hit, which was carried out by the Westies, a murderous Irish gang from Hell's Kitchen anxious to curry favor with the Gambinos.

The shooting came about four months after a union goon squad vandalized a Gambino-linked restaurant to protest the use of non-union labor.

"Like any bully, he couldn't allow a challenge to go unpunished," said the soft-spoken, lanky Cherkasky.

Key evidence in the government's case are tapes of secretly recorded conversations at Gotti's alleged headquarters, the Bergin Hunt and Fish Club. Cherkasky promised the jury the tapes show an angry Gotti seeking revenge on O'Connor and ordering his assault.