Apple is projected to sell 36 million iPhones worldwide in 2010, but Piper Jaffray concedes that total is likely conservative for international sales, and doesn't include the possibility of expansion to other carriers in the U.S.

If Apple does sell 36 million iPhones in 2010, it would be a 40 percent increase from 2009 estimates. In a note to investors Wednesday morning, Gene Munster, senior research analyst with Piper Jaffray, noted that 2010 will mark the first full year of sales with two new carriers in France, Canada and the U.K., and it will also include a full year of sales in China. Sales will be driven by a new iPhone model expected to arrive mid-year.

"We estimated unit figures for the U.S., U.K., France and Germany, then divided the remaining units proportionally by sub count among the remaining carriers," Munster said of his estimates. "The results show that our international iPhone estimates may be a point of conservatism in our model.

"For example, we are modeling for three Russian carriers to sell 1.8M units into a collective sub base of 160M in (calendar year) 2010 vs. AT&T which we estimate will sell 15.8M units to its sub base of 82.5M."

Munster's U.S. estimates don't include projections for a possible Verizon expansion. Currently, AT&T is the exclusive carrier of the iPhone in the U.S. Munster has previously predicted that the Verizon network will be the "next big feature" for the iPhone.

This week, another report speculated that Apple and Verizon are at odds over the pricing of a CDMA iPhone. Recent reports have suggested that a Verizon-capable iPhone could arrive this year.

"We continue to believe that it is highly likely that Verizon will launch the iPhone by the end of 2010," Munster said. "However, Verizon is not in our model and may be a source of significant upside for iPhone units in 2010 and beyond."