<p>SAN FRANCISCO (Reuters) - Sales of Apple Inc's iPhone trumped Wall Street estimates after U.S. shipments soared 51 percent in the third quarter, lifting its stock 5 percent even as profit fell.</p><p>The world's largest technology company said Tuesday that profit fell 22 percent as gross margins slid below 37 percent from more than 42 percent in the year-ago quarter.</p><p>The iPhone's solid showing eased concerns that growing competition is hurting demand for Apple's top-selling product as the global smartphone market matures. Rival Samsung Electronics Co Ltd, which overtook Apple to become the world's largest smartphone maker in 2012, fueled those fears when it issued a disappointing earnings forecast earlier this month.</p><p>Apple's stock, which has fallen 20 percent since January, rose 5 percent to $437.94 in after-hours trade. It closed at $418.99 on Nasdaq.</p><p><a href="http://www.reuters.com/article/2013/07/24/us-apple-results-idUSBRE96M10X20130724">Keep reading...</a></p><p>Read also:</p><p><a href="http://www.nytimes.com/2013/07/24/technology/apple-tops-expectations-on-strong-iphone-sales.html">Apple Tops Expectations on Strong iPhone Sales</a> (New York Times (blog))</p><p><a href="http://www.forbes.com/sites/markrogowsky/2013/07/23/apple-earnings-iphone-sales-dumbfound-the-experts/">Apple Earnings: iPhone Sales Dumbfound The Experts</a> (Forbes)</p><p><a href="http://www.guardian.co.uk/technology/2013/jul/23/apple-profits-second-quarter-iphone-sales">Apple profits drop again but iPhone sales rise</a> (The Guardian)</p><p>Explore: <a href="http://news.google.com/news/more?ncl=dAlgmkl1eUAopHMdmtpur_-5AdEqM&ned=us">953 additional articles.</a></p>