International expansion of the iPhone is the single most important driver of Apple stock in 2010, with overseas sales predicted to account for 80% of all of the company’s handset sales by the end of 2010, according to one analyst — and as reported by “AppleInsider” (

Brian Marshall with Gleacher & Company told clients that he’s increased his 2010 iPad sales estimates to 12 million in calendar year 2010, and 20 million in 2011. More impressive yet, the analyst said that the iPhone is still in the “driver’s seat” for Apple.

Marshall says Apple’s international carrier partners offer a postpaid subscriber base more than six times larger than AT&T, the exclusive wireless carrier of the iPhone in the U.S. Despite that, international sales in calendar year 2009 represented only 60% of total units sold, so there’s nowhere to go but up, up, up.