The sales in the first quarter (Q1) of the U.S. mobile phone market have pushed the Apple’s OS sales to the third place. Not surprisingly, it was Android OS that edged out iPhone’s position to capture its place behind RIM.

As the figures in NPD Group’s reports reveal, iPhone while rooted at 21% of sales in Q1, Android phones have captured 28% of the quarterly markets. The report, which is based on the unit sales, also shows the decline of Blackberry OS sales to 36%.

Still, the Android phones hold just 9% of the total market share against iPhone’s 25.4%. Hopefully, with the current growth rate, Android phones could challenge to iPhone there also.

As it is evident from the report, Android is the only Smartphone OS whose share in sales grew in the last quarter. While iPhone sales share is flat, the rate of other OS including Blackberry, Windows Mobile and WebOS etc. got a decline in theirs.

With Verizon’s new HTC Droid Incredible selling out in its debut week, and HTC EVO 4G expected to hit the markets soon(rumored to be in early June), it looks like there is much more room left for Android sales to grow. Meanwhile, the Apple is expected to release iPhone 4G in early June. This would make the competition between Apple and Google more interesting. Moreover, recent previews of Blackberry 6, acquisition of Palm by HP, and the pending release of Windows Phone 7 also add to the competition among Smartphone OS.

The growth of Android OS is credited to the marketing and sales by the Verizon Wireless. This has boosted the sales of Droid and .Droid Eris, which brought into Android sales to the better position. The OS can also be installed in a wide range of handsets on different carriers as opposed to iPhone’s particular equipment for single carrier. Android being free to hardware manufacturers, they find it a reasonable option than spending money for developing new OS or licensing from others. This gives more flexibility to the OS.

The dramatic growth of Android should have generated an alarm to other OS and as the numbers reveal, the mobile OS from Google is closing the gap to the top place.