The former president of Sega's American division is leaving to join the iPhone game-making startup Ngmoco.

Simon Jeffery had been the president and chief operating officer of Sega for more than four years, but he will become Ngmoco's chief publishing officer and will helm the company's Plus+ Publishing group. The company is one of the top game makers for the iPhone and iPod Touch, and its Plus+ initiatives create an infrastructure framework for developers to promote and integrate social networking features into their games.

"I am delighted to join Ngmoco," Jeffery said in a statement. "It's a very exciting time to be shaping a new games landscape with a super talented team."

The move is another sign that Apple's platform is becoming a significant player in the mobile gaming space. With its 3-D graphics, touch screen, accelerometers, and the App Store distribution center, it's no surprise that Apple's smartphone has been a hit with gamers. The smartphone accounted for about 14% of mobile game downloads in the United States last year, according to a recent report by ComScore.

The platform is only expected to get stronger with this week's release of the iPhone 3G S, which will sport beefier hardware and support for the OpenGL ES 2.0 standard. Additionally, the 3.0 software will add features like push notification, in-app purchasing, and peer-to-peer networking that could have a big impact on iPhone gaming.

The iPhone has multiple barriers to overcome if it's trying to dethrone Nintendo, though. While Apple has sold about 40 million iPhones and iPod Touches, Nintendo's DS and DSi have sold more than 100 million units, with no signs of slowing momentum.

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