BTIG Research has increased its profit estimates for Apple Inc. (NASDAQ:AAPL) on strong iPhone sales in the fourth quarter.

The analyst raised Apple's first-quarter earnings estimate by 50 cents to $10.00, which is above guidance of $9.30 and consensus of $9.83 a share.

Walter Piecyk, an analyst at BTIG, also increased the 2012 calendar year iPhone sales estimate by 17 percent to 125 million from 107 million, as more and more countries enter the sweet spot in the consumer adoption curve of smartphones.

We now believe that Apple sold a record 35 million phones in the calendar fourth quarter based on particularly strong demand in the United States that we estimate will represent nearly 40% of iPhone sales in the quarter, Piecyk wrote in a note to clients.

The iPhone continues to demonstrate strength against a broadening and cheaper lineup of Android phones and waning demand for Blackberry products and could improve further upon the launch of a 4G iPhone, a possible 2012 event.

Recently, Verizon disclosed it had sold 4.2 million iPhones and in early December AT&T referenced strong iPhone sales at the UBS conference which the analyst now estimate translates to sales of 7.0 million iPhones.

The brokerage also raised its estimate for Sprint iPhone sales to over 2.0 million from 1.75 million.  This adds up to more than 13 million iPhones sold in the United States in calendar fourth-quarter 2011, up from its August estimate of 10 million.

The analyst also increased his price target on Apple shares to $580 from $550, based on a $2.50 increase in his fiscal 2013 EPS estimate to $40 and a P/E multiple which he believes is appropriate given the growth that is expected over the next three years.

Shares of Cupertino, California-based Apple closed Monday's regular trading session at $421.73 on Nasdaq.