An off-duty police officer who failed a Breathalyzer test after breaking up an assault “acted correctly” in stopping the crime, Mayor Bloomberg is saying.

“It would have been better if he hadn’t been drinking, but I clearly think the officer did the right thing,” Mr. Bloomberg told reporters at a press conference in Queens yesterday. “He — by accident — saw something where people’s lives were threatened and he took appropriate action.”

Mr. Bloomberg added that he would abide by whatever decision the police commissioner, Raymond Kelly, made regarding the officer’s situation.

The off-duty officer, whose name has not been released, failed a mandatory Breathalyzer test administered after he shot a suspect, registering a blood-alcohol level of .09, according to the New York Post. The legal measure of sobriety in New York State is .08.

The police department said the officer has been placed on modified duty and relieved of his firearm. The alcohol testing policy was put in place last year after the fatal shooting by police officers of Sean Bell in 2006. The Patrolmen’s Benevolent Association opposes the measure, arguing that it is unconstitutional and discourages off-duty officers from intervening in crimes.

The incident involving the officer occurred at about 2 a.m. on Sunday, when he encountered a gang of four men assaulting someone in Queens. After identifying himself as a police officer and attempting to break up the assault, one of the men, Stephon Allston, 22, shot at the officer, who fired back and hit Mr. Allston in the leg and arm, police said. Mr. Allston fled but was eventually arrested and charged with attempted murder.