Galaxy S4 launched

Samsung Electronics is the world leader in smartphone sales, besting Apple in many countries. Now Samsung of South Korea is stepping up its challenge to Apple, bringing the battle to its rival's home turf.

At a news conference in New York on Thursday, its first American promotional event for its flagship smartphone, Samsung showed off the Galaxy S 4, which has a screen slightly larger than the latest iPhone.

The device has quirky software features, including Smart Scroll, in which the front camera detects when someone is looking at the phone, and scrolls the screen according to the angle the phone is tilted. The phone can also be controlled with hand gestures. Waving a hand down in front of the phone will scroll up on a Web page, for example.

"Once you spend time with the Galaxy S 4, I'm very confident you'll find how its innovations make your life simple and fuller," said JK Shin, president of Samsung Mobile Communications.

With the prominent introduction of the phone, Samsung is trying to end its role as understudy to its more celebrated competitor, especially in the crucial American market, where Apple still rules. Even as Samsung has surpassed Apple in global market share, it is often criticized in the United States as an effective copycat, taking most of its product cues from Apple. But Samsung has begun flexing its marketing muscle more aggressively here to try to change that perception.

"This is Samsung's time right now," said Gene Munster, an analyst at Piper Jaffray. "They are clearly gaining more attention this time around than they ever have."

Apple itself is showing signs of concern. In an unusual move on the eve of the Samsung event, Philip W. Schiller, Apple's senior vice president for worldwide marketing, gave several interviews in which he discussed flaws in mobile devices based on Android, the Google operating system used by most of Samsung's smartphones.

But Apple still has many big advantages that allow it to defend its position in the mobile business. Its iPhone 5 was the best-selling smartphone in the world in the holiday quarter, even though Samsung's vast portfolio of phones is bigger than Apple's. By charging a premium for its products, Apple raked in 69 percent of the profits in the smartphone business last year, compared with 34 percent for Samsung, according to a report by T. Michael Walkley, an analyst with Canaccord Genuity.

While analysts like Munster expect Samsung to gain market share in the United States in the coming two quarters, they predict Apple is likely to still dominate the crucial holiday shopping season, when gift shoppers buy mobile devices in droves. That is when sales of the iPhone typically outperform all other devices. By unveiling its flagship phone just before spring, Samsung is striking at Apple months before a new iPhone is expected to be released.

"Everyone stays out of the zone of iPhone launch periods," said Horace Dediu, a blogger and analyst with Asymco.

Apple's iPhones fly off the shelves in the United States, but Samsung is still the top seller of smartphones worldwide. And in the United States, Samsung is gaining.

In the fourth quarter of 2012, sales of Samsung devices accounted for 30 percent of the American smartphone market, up from 21 percent the previous year, according to NPD Group, the research firm. For the same time period, Apple's iPhone accounted for 39 percent of the market, down from 41 percent the previous year.

Samsung is far exceeding Apple in its rate of growth worldwide. In the holiday quarter last year, Samsung shipped 63.7 million smartphones, up 76 percent from the previous year, according to IDC, the research firm. Apple sold 47.8 million, up 29.2 percent from the previous year.