Apple's iPhone sales are sputtering as rival smartphone makers ramp up their offerings, a market research firm said Wednesday.

The survey by IHS iSuppli said smartphones are still going strong around the world, but that Apple is lagging.

"Apple's iPhone franchise appears to be stalling as first-quarter shipments of 37.4 million fell below expectations," the report said.

"With the next iPhone model not expected until the second half of the year, there is a real possibility that the full-year 2013 sales volume of the iPhone may be essentially flat at around 150 million units, compared to 134 million units in 2012."

IHS analyst Wayne Lam said the volume of new flagship smartphones from top manufacturers this year "has been astounding," citing the new BlackBerry Z10, HTC One, and updated Samsung Galaxy S4.

"The possible slowing growth of the iPhone and the rapid pace of competitive smartphone releases speak to the ferocious nature of the handset business, especially now as the market continues to pivot from a market dominated by lower-end handsets known as feature phones to one that is increasingly smartphone-centric," Lam said.

IHS said smartphones are likely to make up more than half of the 1.5 billion handsets sold in 2013. It said that by the end of 2013, the number of mobile subscribers worldwide is projected to reach seven billion, an increase of 6.5 percent from the end of 2012.

Recent surveys have shown Google's Android operating system is used on around three-fourths of new smartphones. Apple's iOS accounts for around one-fifth of the worldwide market.

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