New York residents will soon be able to call 311 for help obtaining information about social services, Mayor Bloomberg announced yesterday at the city’s 311 Customer Service Center in Lower Manhattan.

The expanded service, which launches in May and will be the largest of its kind in the country, will connect callers to nearly 1,000 social services through about 1,300 nonprofit organizations and will be accessible 24 hours a day, seven days a week.

“The key is to use 311 to link people more quickly and directly to the governmental agencies and nonprofit groups that provide much of the frontline help and human services in our city,” Mr. Bloomberg said. He used combating hunger as an example of its use, saying those in need of a meal could call 311 for help locating a food pantry or information about applying for food stamps.

The city will launch a $250,000 ad campaign in English, Spanish, Chinese, Arabic, Haitian Creole, Korean, and Russian that will run in subways and bus shelters to publicize the new features.

Social services help is presently available under the number 211 in many other municipalities and states, and some lawmakers, including Senator Clinton, have called for the adoption of a national 211 number. Mr. Bloomberg promised to incorporate 211 into the city’s 311 service during his 2005 re-election campaign, saying the two features would be more effective if consolidated into a single phone number. The city’s 311 service, which was launched in 2003, receives about 41,000 calls a day and provides information about government services.