Research in Motion Ltd's BlackBerry Curve moved past Apple Inc's iPhone in the first quarter to become the best-selling consumer smartphone in the U.S., research group NPD said on Monday.

RIM, which already dominates the corporate smartphone market in the United States, also had three of the top five best-selling consumer smartphones in the period, with the Storm at No. 3 and the Pearl at No. 4, NPD said.

T-Mobile's G1 ranked No. 5.

The iPhone was the top-selling consumer smartphone in the U.S. in both the third and fourth quarters of 2008. The Curve was second and Palm Inc.'s Centro was third.

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NPD credited a "buy-one-get-one" promotion by Verizon Wireless — a joint venture between Verizon Communications Inc and Vodafone Group Plc — for helping push the Curve past the iPhone.

"The more familiar, and less expensive, Curve benefited from these giveaways and was able to leapfrog the iPhone, due to its broader availability on the four major U.S. national carriers," said Ross Rubin, director of industry analysis at NPD, in a news release.

The iPhone is only available through AT&T Inc. Apple launched its second-generation 3G iPhone last July.

RIM's consumer smartphone market share climbed 15 percent from the previous period to nearly 50 percent in the first quarter, as Apple's and Palm's share both fell 10 percent.

More than half of RIM's 25 million subscribers now fall into the non-corporate category, according to the company.

But the smartphone battle is just starting to heat up. Apple is widely expected to unveil a new iPhone in the next few months, while Palm's highly-anticipated Pre smartphone is set to launch during the second quarter.

The smartphone market as a whole continues to grow, even as the larger handset market stagnates.

The devices made up 23 percent of U.S. handset sales in the first quarter, NPD said, up from 17 percent in the year-ago quarter.

Shares of Waterloo, Ontario-based RIM rose 3 percent in late afternoon trading on the Nasdaq to $74.43. Shares of Cupertino, California-based Apple were up 3.4 percent to $131.63 on the Nasdaq.