By Noel Randewich

SAN FRANCISCO, Nov 6 (Reuters) - Qualcomm Inc on Wednesday forecast revenue below expectations and said it would curb fast-growing operating expenses, stoking concerns the leading mobile chipmaker faces tough competition in Asia, and sending its stock down.

San Diego-based Qualcomm's components are used in smartphones made by Apple Inc and Samsung Electronics Co Inc and its patents pull in revenue from licensees across the cellphone industry.

But with growth in the smartphone industry shifting away from wealthy markets such as the United States and toward China and other emerging economies, analysts have been concerned that less expensive phones could impact Qualcomm's profitability.

Qualcomm posted double-digit growth in the fiscal fourth quarter for the 13th consecutive time, but its revenue forecast suggests the company's explosive growth in recent years might be slowing as smaller competitors challenge it in Asia.

"We know you can't get the same royalty revenue off of a sub-$200 phone that you get off an iPhone or the Galaxy line," said Williams Financial analyst Cody Acree. "We're seeing evidence that the emerging-market impact is having pressure on revenue and earnings trends and it's forcing the company to react and cut its spending."

Qualcomm said it operating expenses in fiscal 2014 would grow between 5 percent and 7 percent, much less than the 20 percent annual growth seen in the past three years.

CEO Paul Jacobs said Qualcomm has been releasing new chips faster than its top-tier smartphone customers could adopt them, and that in future chips would be launched a little less often as the company focuses more on less expensive devices.

"What we're trying to do is focus on the highest-growth opportunities," Jacobs told Reuters. "We are investing heavily in the low end of the market to get our cost structure into a better place."

He said Qualcomm is also focusing on new markets such as "connected homes" decked out with growing quantities of sensors and communications chips in thermostats, locks and power switches.

In September, Qualcomm unveiled its "Toq" smartwatch, which Jacobs hopes will stoke interest in the company's always-on, low-power display technology and push manufacturers to make similar devices.

For fiscal 2014, Qualcomm expects the average selling prices of phones using its CDMA technology to be between $216 and $230, down about 1 percent from 2013.

Average prices for cellphones in the June quarter, used to calculate licensing revenue for Qualcomm in the September quarter, were between $227 and $233, the company said.