As Apple continues to sell iPhones all over the globe, Google is preparing to launch new options for advertisers to target iPhone owners directly.

In meetings with various agencies, Google has presented a new option to show context-sensitive search ads from iPhones. The change, expected to be finished shortly, means advertisers will be able to create an iPhone ad group as part of their regular search campaign, according to agency executives briefed about the modification.

Google had little to say officially about the program, though some inside sources have confirmed that it is being readied.

The move highlights Apple’s growing clout in the mobile ad market, as well as the challenges raised by iPhone for marketers.

For instance, American Airlines could use the new Google option to change a search ad from a phone call to action to click to one driving a phone call to reservations. Or the ad could immediately highlight the airline’s iPhone-optimized site for booking flights. It could provide a whole new gateway to selling services to prospective customers.