LOS ANGELES (AP) Mayor Antonio Villaraigosa on Tuesday signed one of the nation’s toughest laws on pet sterilization, requiring most dogs and cats to be spayed or neutered by the time they are 4 months old.

The ordinance is aimed at reducing and eventually eliminating the thousands of euthanizations conducted in Los Angeles’ animal sheltersevery year.

“We will, sooner rather than later, become a no-kill city and this is the greatest step in that direction,’ Councilman Tony Cardenas said as he held a kitten at a City Hall news conference.

Councilman Richard Alarcon, who like Cardenas is a co-author of the bill, brought his two pet Chihuahuas to the event to be neutered in a van operated by the city.

The ordinance does exempt some animals, including those that have competed in shows or sporting competitions, guide dogs, animals used by police agencies and those belonging to professional breeders.

The average pet owner, however, must have their dog or cat spayed orneutered by the time it reaches 4 months of age (as late as 6 months with a letter from a veterinarian). People with older unneutered pets and newcomers to the city with animals also have to obey the law.

First-time offenders will receive information on subsidized sterilization services and be given an additional 60 days. If they still fail to comply they could be fined $100 and ordered to serve eight hours of community service. A subsequent offense could result in a $500 fine or 40 hours of community service.

The ordinance brings the nation’s second-largest city into line with about a dozen of its neighbors that have similar laws.

Many states require animals adopted from shelters to be sterilized, and New York City requires the same for animals bought from pet shops, but restrictions such as those in Southern California are rare. A 2006 Rhode Island law requires most cats to be sterilized.

A measure similar to Los Angeles’ passed the California Assembly last year but did not gain state Senate support.

Los Angeles animal shelters took in 50,000 cats and dogs last year and euthanized approximately 15,000 at a cost of $2 million, according to city officials.

Bob Barker, the retired game-show host who famously ended every ‘Price is Right’ show with a call for sterilizing pets, pushed for the law’s adoption and was among those at Tuesday’s news conference.

The next time that you hear me say, ‘Help control the pet population, have your pet spayed or neutered,’ I can add, ‘It’s the law in Los Angeles,” a jubilant Barker said.