Apple Inc. (Nasdaq: AAPL) may not release the next model of its iPhone until late September or October, which would lead to slower September sales, said Oppenheimer & Co. analyst Ittai Kidron as he cut his price target on the company.

Kidron, who maintained his “outperform” rating on Apple, reduced his 12 to 18 month target on the stock to $420 from $450 and his expectations for iPhone sales in the quarter ending in September to 19 million units from 20.5 million units.

Apple became the fourth-largest mobile-phone maker by unit shipments last quarter after entering the handset market with the debut of the iPhone. Apple accounted for 5 percent of shipments, up from 2.8 percent a year earlier, according to researcher IDC. The success of the iPhone and the iPad tablet helped Apple supplant Microsoft Corp. (Nasdaq: MSFT) as the world’s most valuable technology company last year.

“We’ve been modeling a full month of new iPhone sales in September and now believe it’s more prudent to model a late September, October launch,” he wrote in the note. “This suggests possible modest quarter-on-quarter growth trends in September, and not the strong growth we previously modeled.”

Apple rose $6.01, or 1.9 percent, to $321.33 at 10:38 a.m. New York time in Nasdaq Stock Market trading. Before today, the stock had dropped 13 percent from its 52-week high on Feb. 16.

Kidron also wrote that a less expensive “mini-iPhone” is critical to Apple expanding its smartphone market share.

A slowdown in iPhone sales growth may also hurt Apple’s profitability as iPads, which have smaller profit margins than iPhones, become a greater percentage of the overall sales, Kidron said.

“While good iPad demand is a positive, a heavier mix of iPads means margin pressure,” he wrote.

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