The latest report released by the research firm Strategy Analytics on Wireless Smartphone Strategies says that although Android still dominates the mobile OS market in the U.S., its market share declined over the last year. On top of that, while Android lost its grip on the market significantly, rival Apple's iOS platform grew rather rapidly during the same time period.

The report revealed that in the second quarter of 2012, Android's market share dropped from 60.6 percent a year ago to 56.3 percent of the Smartphone Operating System market in the U.S. Android's change over the year turned out to be more than 4 percent in total, while Apple's iOS rose by 10 points from 23.2 percent in the second quarter of 2011 to 33.2 percent this year.

Neil Mawston, Executive Director at Strategy Analytics said that the Cupertino tech giant's highly anticipated next gen iPhone, dubbed the "iPhone 5," would further help iOS to gain more ground on the mobile OS market.

"Apple is rumored to be launching a new iPhone in the coming weeks, and that event, if it takes place, is going to heap even more pressure on Android in its home market," said Mawston.

According to a report by Android Authority, the plunge in Android sales happened prior to the launch of the Samsung Galaxy S3 in the U.S., meaning that "Android will probably go over 60 percent again in Q3, and then will probably drop again in Q4 when the next iPhone will be launched."

"It is possible that in the future Android might not be able to maintain its 60 percent market share in the U.S., and will perhaps have a hard time staying over 50 percent as well," the report added.

Source: Strategy Analytics

The third in the list was BlackBerry OS, which also saw a decline in the market share. The OS was listed with a dropped market share of 6.5 percent for the Q2, 2012, compared to the 10.5 percent of the market last year.

"Consumers, businesses and operators continue to be frustrated by Blackberry's limited toushcreen smartphone portfolio and repeated delays to its new BB10 operating system," said the report.

The rest of the market that includes Windows Phone was just 4 percent, dropping from mere 5.7 percent during the same period last year.

When it comes to smartphone shipments, the total number of shipments fell 5 percent annually to reach 23.8 million units in the U.S. in Q2, 2012. In the second quarter last year, the total number of smartphones shipped was 25.2 million.

According to the report, of the 23.8 million units shipped during Q2 this year, 13.4 million belong to Android (15.3 million units last year), 7.9 million to iOS (5.9 million units last year), 1.6 million to BlackBerry OS (2.7 million units last year) and the remaining 1 million units to other players (1.4 million units last year).

"This was one of the slowest growth rates ever experienced by the important US smartphone market. A volatile economy, maturing penetration of smartphones among contract mobile subscribers, and major operators tightening their upgrade policies to enhance profits were among the main causes of the slowdown," said Alex Spektor, Associate Director at Strategy Analytics.

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