* Android gaining momentum -Schmidt

* Top-selling phones winning market share -NPD

LAKE TAHOE, Calif., Aug 4 (Reuters) - About 200,000 smartphones based on Google's GOOG.O Android operating system are sold every day, CEO Eric Schmidt said on Wednesday, underscoring the strong challenge to rivals like Apple's AAPL.O iPhone.

Schmidt told reporters on the sidelines of an industry conference in Lake Tahoe that Android -- a mobile software launched just over a year ago -- was gaining momentum in a fiercely competitive tech arena.

Smartphones running the fledgling software topped the list among U.S. consumers in the second quarter, industry tracker NPD said on Wednesday. The operating system powered a third of all smartphones sold from April to June, with Research in Motion's RIM.TORIMM.O BlackBerry sliding to second place for the first time since 2007. [ID:nN04255464]

BlackBerry lost 9 percentage points of market share, diving to 28 percent. The iPhone came in third with 22 percent.

Android is now on smartphones made by a number of different manufacturers, including a revitalized Motorola's MOT.N Droid -- the best-selling Android handset in the second quarter among U.S. consumers -- and Taiwan's HTC 2498.TW.

Google said recently that 160,000 Android phones had been activated each day during the second quarter, up from 65,000 in the first quarter. (Reporting by Alexei Oreskovic)