Add AT&T to Yahoo’s growing list of carrier partners that have agreed to promote Yahoo oneSearch as their preferred mobile search engine.

The AT&T deal comes just two weeks after published reports circulated that Google and Verizon were close to a deal that would make the search king Verizon’s preferred mobile search engine. (see Google, Verizon Connect on Mobile Search)

At stake for both carriers and search firms is a piece of a projected $221 million in total worldwide mobile search ad revenue in 2008. That total is expected to grow to $2.3 billion by 2011, according to eMarketer.

The deals give the search firms “beachfront property” as the on-deck search tools on the carriers’ mobile phones. In return the carriers get the benefit of attractive search algorithms designed to optimize search revenues.

To date Yahoo leads the race for preferred positioning among carriers with more than 60 deals compared to 40-plus for Google.

But AT&T is the first U.S. carrier to choose Yahoo as its preferred mobile search engine.

Yahoo’s major carrier successes have come mainly in Europe and Asia. Last February, the search company unseated Google as T-Mobile’s preferred mobile search engine. (see Yahoo Scores Search Victory over Google)

And in June Yahoo announced mobile search and advertising deals with seven Asian carriers including Mahanagar Nigam Ltd. of India and Hong Kong CSL Ltd. (see Yahoo Mines Mobile Gold in Asia)

Unlike rival Google, Yahoo has a long track record of carrier partnerships dating back to its Internet portal arrangements a decade ago with both AT&T and Verizon.

Google has provoked some ill will among mobile carriers because of its lobbying effort to promote open mobile networks, and its participation in a recent spectrum auction in the U.S.