Yahoo and AT&T began a planned partnership on Monday that brings the search engine's mobile-centric search platform to the carrier's customers.

AT&T has worked with Yahoo for quite some time, extending back to 2001 when the company signed a shared-revenue agreement for the telco's broadband services in select areas. And since February 2006, AT&T's wireless arm -- then Cingular -- has had a standing agreement with Yahoo.

OneSearch melds all of the search engine's disparate services into one application. Users can search for information based on a location, as well as use Flickr, and check their e-mail.

The mobile announcement is part of a January deal which encompassed all of AT&T's telecommunications services. Yahoo is now the search provider of choice for AT&T's TV, mobile, and Internet services.

AT&T is just one of about five dozen wireless carriers worldwide offering OneSearch to subscribers. Yahoo's potential reach is about 800 million, which is about 40 percent of all worldwide wireless customers. However, only about two-thirds of the announced carriers are actually offering the service to customers. There is no word as to when Yahoo expects the rest of the carriers to come online.

Yahoo is also working with Verizon -- however, that deal is only for its broadband Internet customers. Google is currently in discussions with the carrier to provide its search services to Verizon Wireless customers.