Within a year, New Yorkers needing food stamps, job training, or other social services will be able to find answers to their questions by calling a single number, 311.

Standing in the 311 headquarters in Lower Manhattan, Mayor Bloomberg yesterday announced the expansion of the 311 Citizen Service Center. It was the first plan proposed during his campaign that he now is turning into action.

“This major expansion of the 311 system will allow us to provide information and referral assistance to New Yorkers on the city’s vast network of city agencies, nonprofit providers, community-based organizations, and religious organizations,” Mr. Bloomberg said.

The new system will cost $10 million in capital dollars. The city also has already budgeted $12 million to subsidize the service’s referrals, which will be conducted by United Way, the organization with which the city will coordinate the new effort.

Also, Mr. Bloomberg pointed out that the new system would save time and resources at a number of city agencies.

“You will see a lot of savings throughout the system because people won’t be going to agencies of the city government and requesting things that the city government doesn’t provide anymore,” he said. “A counselor will be better able to direct you, whether to a city agency or to one of the other nonprofits.”

The new service will open up the United Way’s list of more than 2,500 nonprofit health and human services agencies to the public. The agencies operate more than 15,000 programs from more than 7,200 sites throughout the five boroughs.

The city’s Human Resources Administration commissioner, Verna Eggleston, who has worked in the nonprofit world as well as for the city, said New Yorkers have been waiting for a system like this one for a long time.

“When an individual or a family is in crisis, they should be able to make one call, and that call should lead them to the service that they need, whether it comes from a city agency or a nonprofit organization,” she said.

The plan received positive initial feedback.

“Every day, people come into my district office looking for help, so I fully understand the dire need for an easily accessible phone number that people can call to get whatever services they require,” the chairwoman of the City Council’s Committee on Technology and Government, Gale Brewer, said. She had only one caution: “I urge the mayor to ensure that the confidentiality of every resident is provided.”

The mayor predicted the center would field a million calls a year. The existing call center receives 43,000 calls a day.