Three months after taking the lead in PC shipments, China has passed the U.S. as the world's top smartphone market.

Shipments to the Sino superpower reached a record 23.9 million in the third quarter, a 58% sequential increase, researcher Strategy Analytics reports. U.S. shipments fell 7% to 23.3 million over the same period. Increasing retail availability plus deals with carriers China Mobile (NYSE: CHL) and China Unicom (NYSE: CHU) have made it easier for consumers to purchase smart handsets.

Nokia (NYSE: NOK) leads the Chinese market with 28.5% of shipments in Q3. Samsung, whose Galaxy lineup has become the face of the Android operating system in many parts of the world, ranked second with a 17.6% slice of the market.

Apple (Nasdaq: AAPL) wasn't ranked in Strategy Analytics' press release, but according to The Wall Street Journal, the firm said the iPhone could gain substantial share if China Telecom (NYSE: CHA) were to introduce a localized version of the 4S handset that's set sales records here in the United States.

Stateside, HTC leads all handset makers in terms of smartphone shipments with a 24% share of shipments made in Q3. The iPhone ranked second with a 20.6% share. Neither Nokia nor Research In Motion (Nasdaq: RIMM) put up U.S. numbers worthy of being mentioned in Strategy Analytics' press release. Shocking.

How does all this play out for the long term? That's tough to say, but right now, Microsoft (Nasdaq: MSFT) and Nokia look smart for applying resources to win customers in China. Strategy Analytics' findings may also help explain why many believe Apple's mobile growth opportunity remains largely untapped. (For example, Morgan Stanley says 67% of Asian carriers lack the iPhone.)

Maybe that's the good news in all this. The U.S. may be fading in the fight to be the world's top tech market, but U.S. tech companies have rarely been in better shape.

Who do you think wins the mobile melee in China? Would you buy shares of Nokia, Apple, or neither? Please let us know what you think using the comments box below. You can also add Apple or Nokia to your watchlist for instant updates when mobile news breaks.