AT&T is in negotiations with Apple to extend its exclusive deal to carry the iPhone in the U.S. from 2010 until 2011, The Wall Street Journal reported, citing people familiar with the matter.

For Apple, however, continuing the exclusive agreement with AT&T seems less advantageous as time goes on, as selling the iPhone through various carriers would increase the number of devices sold in the U.S.

Since the iPhone launch in 2007, AT&T is estimated to have sold roughly 17 million handsets in just in just two years. In the second half of 2008, AT&T added 4.3 million iPhone subscribers, 40 percent of whom were new customers for AT&T.

It is still unclear how much AT&T is willing to pay to hold onto its to be the sole seller of the iPhone.