By Chris Ciaccia

Apple (AAPL) is under attack again Friday as Credit Suisse cut earnings estimates, citing iPhone worries.

Analyst Kulbinder Garcha cut his earnings estimates on the company, but kept the "outperform" rating as he believes Apple will refresh its iPhone lineup in the second half of 2013 that will "return Apple to its growing ways." He now expects 30.6 million iPhones to be sold in the second quarter of 2013, due in large part to a mid-2013 iPhone refresh, which may cause some hesitancy on consumers.

In the past, Apple has blamed lower sales or delayed purchases on consumer speculation about products.

Garcha also mentioned the impact from Samsung, which is set to launch the Galaxy S IV on March 14 in New York. 

Apple and Samsung have been battling for the top spot in smartphones, with various research firms citing one company or the other leading at various times. Garcha noted the Galaxy S IV is likely to gain share in the high-end, where Apple competes with its iPhone 5.

There's also the concern that larger smartphones are taking more market share. At Mobile World Congress, Garcha noted that approximately 70% of the phones unveiled are geared toward high-end consumers, with 60% of them having bigger screens than the iPhone 5, which is 4 inches.

Even with all of these concerns, the iPhone is still a growth story, and continues to be the major driver of profits for Apple. Last quarter, Apple sold 47.8 million iPhones, up from 37.04 million iPhones in the year-ago quarter. That amounted to 37.1% year-over-year growth, not counting the extra week in the fiscal first-quarter of 2012 because of the leap year.

"We would view the above reduction in volume forecasts as a reset and product transition impact rather than a structural concern long term," Garcha wrote in his report.

There are additional carriers which could add as many as 65 million iPhones in fiscal 2013. TheStreet reports that China Mobile (CHL) has been in talks with Apple, presumably about the iPhone. "In the morning, Apple's CEO Tim Cook visited China Mobile's headquarters. China Mobile's Chairman Xi Guohua and Tim Cook discussed matters of cooperation," a China Mobile spokesman told Reuters last month, though a confidentiality agreement was signed.

Shares of Apple were lower in premarket trading Friday, off 0.73% to $438.19.

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