It's now the law, pet owners who live in Los Angeles must have their dogs and cats sterilized by the time the animals are 4 months old.

The ordinance, signed into effect Tuesday by Mayor Antonio Villaraigosa, is aimed at reducing and eventually eliminating the thousands of animals that are euthanized in the city's animal shelters every 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.

One of the ordinance's sponsors, Councilman Richard Alatorre, brought his two pet Chihuahuas to the event to be neutered.

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 or neutered by the time it reaches 4 months of age (as late as 6 months with a letter from a veterinarian).

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.

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.

Longtime animal-sterilization advocate Bob Barker of "Price is Right" fame 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.

Minus four members, the council voted 10-1 in favor of the ordinance. A second vote on the measure is required before it can become a city law.