Nintendo&39's DS is losing market share to iOS and Android.

Nintendo is facing increased pressure from smartphones and tablets in the gaming arena.

According to a new report from research firm Flurry Analytics, Nintendo's share of the portable gaming market in the U.S. slipped from 70 percent in 2009 to 57 percent in 2010. Sony's PlayStation Portable, meanwhile, saw its market share figures drop from 11 percent to 9 percent year over year. The big winners in 2010, according to Flurry, were iOS- and Android-based devices, which nabbed 34 percent of the portable gaming market. In 2009, Apple's iOS had just 19 percent market share.

Flurry's findings further cement the reality of Nintendo's somewhat tenuous position in portable gaming. Although its DS was still wildly popular last year and its brand-new 3DS has seen strong initial sales, gamers are increasingly turning to their smartphones to play casual titles like Angry Birds. Moreover, with $39.99 3DS games on store shelves, some folks are finding it difficult to choose those titles over the free or sometimes $1 or $2 games available in Apple's App Store and the Android Market.

Those worrisome market factors have already caught the attention of Nintendo. In October, Nintendo of America president Reggie Fils-Aime said that he believes Apple and its App Store are a bigger threat to Nintendo's business right now than Microsoft's Xbox 360, which has been slowly gaining on Nintendo's Wii.

"Do I think that in the near term [Apple] can hurt us more than Microsoft" Nintendo of America President Reggie Fils-Aime said to Forbes in an interview last year. "Absolutely."

Though iOS and Android devices are taking a bite out of the portable gaming market, they have a long way to go to catch up to consoles, Flurry found. The company said that console games made up 76 percent of all gaming software revenue in the U.S. last year, up from the 71 percent market share they nabbed in 2009. Portable gaming devices, like the DS and PSP captured 16 percent market share, while iOS and Android were only able to muster 8 percent market share.

All told, consumers in the U.S. spent $10.7 billion on games last year. iOS and Android game revenue was $800 million.