Apple shares edged lower 0.1 percent to $608.85 in premarket trading.

For the December quarter, Apple forecast revenue of $52 billion, below estimates of $55 billion, according to Thomson Reuters I/B/E/S. It expects margins of 36 percent, far lower than analysts' expectations of 43 percent.

Analysts focused on the decline in margins and played down the significance of a fall in iPad sales in the last quarter, as users waited for the iPad mini, and they did not expect this to continue.

Apple's forecast decline in gross margin, even assuming it was deliberately aiming low, still pointed to an unusual decline, Evercore Partners analysts Rob Cihra and Edison Yu said in a research note. Evercore cut its price target on the stock to $775 from $800.

Nomura Equity Research said it expected production costs to rise in the current quarter, after Apple redesigned so many of its products at once.

"The iPhone 5, iPod Touch, iPod nano, iPad mini and iMac all feature new form factors and our checks with the supply chain indicate that many of these are very complex to manufacture and are likely resulting in reduced production efficiencies," Nomura analysts said in a note as they lowered their price target to $660 from $710.

Apple heads into the current quarter after refreshing almost all of its product lines, including introducing a lower-priced 7.9-inch "iPad mini" and an upgraded fourth-generation full-sized iPad.

Apple said it expects 80 percent of revenue in the current quarter to come from new products but did not increase the product prices to offset higher costs and maintain its margins.

Analysts, however, expect gross margins to recover by June next year as rising volumes trim manufacturing and component costs.

When the iPhone 4 was launched, Apple suffered a 480 basis point decline in corporate gross margins but it recovered entirely within two quarters, Raymond James analyst Tavis McCourt said.

He cut his price target on the stock by $30 to $700.

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Apple had struggled to deliver large quantities of the iPhone 5 since its launch in late September, with waiting times stretching at times to three weeks in some regions.

This week, AT&T Inc blamed its disappointing subscriber growth in the third quarter on a shortage of iPhone 5, highlighting its dependence on Apple.

Apple CEO Tim Cook told analysts on a conference call that there was a heavy backlog for the latest iPhone but the company had mostly worked out kinks in its supply chain.

"We believe initial demand continues to look huge for Apple's new 6th-gen iPhone 5, seeing a big jump coming in this Dec-qtr where our estimate remains unchanged at 49 million iPhones," Evercore said.

South Korean rival Samsung Electronics Co posted a fourth straight record quarterly profit, $7.4 billion, with strong sales of its Galaxy range of phones.

Samsung sold 56.3 million smartphones in the third quarter, according to research firm IDC, giving it a global market share of 31.3 percent -- more than double that of Apple, which said it sold 26.9 million iPhones.

Although fourth-quarter iPad sales of 14 million missed estimates, analysts said they expected sales growth in the December quarter and 2013.

Evercore forecast Apple to ship 67 million for 2012 and 97 million next year, and said this would said this would take sales of the tablet to around 27 percent of the size of the traditional PC market in 2013.

(Reporting by Supantha Mukherjee in Bangalore)

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