Google's mobile operating system Android is losing market shares to Apple's iOS in the United States, fresh stats released by Strategy Analytics revealed.

According to the released figures, Google's Android suffered a year-on-year loss of 4 per cent in its market share to 56 per cent in the second quarter of 2012.

This was the second quarter in row when Android's market shares slipped.

The shipments of Android-based handsets also slipped, from 15.3 million in the second quarter of 2011 to 13.4 million in the corresponding quarter of this year.

Apple's iOS, Android's biggest rival, enjoyed an increase of 10 per cent, from 23 per cent in the second quarter of 2011 to 33 per cent in the second quarter of this year.

Shipments of Apple iPhones in the United States jumped 2 million, from 5.9 million to 7.9 million, in the same time period.

Overall smartphone shipments slipped 5 per cent in the country. Strategy Analytics' Associate Director Alex Spektor held a number of factors responsible for the decline in shipments, including volatile economy, carrier's stricter upgrade policies, and maturing penetration of smartphones among contract mobile subscribers.