Google's (NASDAQ:GOOG) Android operating system commanded 43.7 percent of U.S. market share through August, gaining almost 2 percentage points from comScore's last count of 41.8 percent in July, according to the researcher.
Android sales could get a boost in the U.S. from sales of the new Samsung Galaxy S II Android 2.3 Gingerbread smartphones on AT&T, Sprint and T-Mobile.
Verizon Wireless meanwhile is expected to begin selling the Samsung Nexus Prime Android 2.4 "Ice Cream Sandwich" handset after the OEM and Google introduce it next week at CTIA in San Diego.
Apple's (NASDAQ:AAPL) iOS share rose modestly to 27.3 percent from 27 percent in July and 26.6 percent in June, said comScore.
The iPhone should see a much bigger boost through November and December after Apple launches the iPhone 4S Oct. 14 on AT&T (NYSE:T), Verizon Wireless (NASDAQ:VZW) and Sprint (NASDAQ:S). The new phone features a faster A5 processor, 8-megapixel camera, iOS 5 and iCloud integration, as well as the Siri virtual assistant application.
Piper Jaffray expects Apple to ship 25 million iPhones in the December quarter, padding the company's current worldwide sales of over 128 million iPhones.
Android and iOS' share gains continued to come at the expense of Research in Motion's BlackBerry OS, whose share dropped 2 percentage points to 19.7 percent in August from 21.7 percent in July, after falling from 23.4 percent in June and 24.7 percent in May.
RIM's (NASDAQ:RIMM) BlackBerry Bold 9900/9930 models clearly aren't making a major dent in consumer purchasing. Meanwhile, Microsoft (NASDAQ:MSFT) Windows growth remained flat at 5.8 percent.
However, the company is bullish on new phones that incorporate the fresh Mango build of Windows Phone 7, the company's next-generation smartphone platform. Nokia (NYSE:NOK) is betting its company on the platform to save its foundering fortunes.
As for phone OEMs, Samsung continues to lead, with 25 percent of the U.S. market. LG is second with 21 percent, followed by Motorola Mobility and its 14 percent share. Apple is approaching 10 percent with its iPhones, while RIM fell to 7 percent.
Overall, some 85.5 million U.S. folks had smartphones through August, up from 82 million in July, and up 10 percent from the previous three-month period.