Android gains momentum as iPhone showdown approaches

While the world awaits Apple’s (s aapl) next iPhone, the Android (s goog) smartphone juggernaut continues to gain momentum, according to new figures from Nielsen. Android smartphones accounted for 43 percent of all smartphone owned in the U.S. as of August, up from 40 percent in July. And among recent purchases within the past three months, 56 percent of them have been Android devices, said Nielsen, which presented the data at GigaOM’s Mobilize Conference.

The iPhone continues to hold its ground with 28 percent of both the entire smartphone market share and recent acquisitions. RIM (s rimm), meanwhile, slipped in overall U.S. market share to 18 percent, down one percentage point from 19 percent in July while it has 9 percent of recent acquisitions.

These figures could change quickly with the arrival of Apple’s next iPhone. With the usual annual summer iPhone launch pushed back at least into fall, it’s likely that there’s a lot of pent up demand for the next model. And with the device expected to debut on Sprint¬†(s s), it should open up even more sales opportunities.¬†Apple, in fact, has to be pretty confident, considering it hasn’t lost any ground even with an aging iPhone 4 still selling well against an army of much newer Android devices.

But the Nielsen figures show that the Android train has kept on chugging and may have benefited from a later start for the next iPhone. A recent Nielsen survey found that among consumers expecting to buy a smartphone in the next year, both Android and iPhone got about one-third of the consumers. But without a new iPhone to buy, some smartphone buyers may have sprung for an Android. It will be interesting to see how the market changes with an iPhone available on three of the top carriers in the U.S. Apple got a boost when the iPhone debuted on Verizon(s vz) and could see another increase, though probably not as big, when it launches on Sprint.

And the entire smartphone market continues to grow with 43 percent of all devices now smartphones, up from 40 percent in July. Among recent purchases within the last three months, smartphones now make up 58 percent of all mobile phone buys. That means we’re continuing to inch closer to the day when smartphones will make up more than 50 percent of all mobile phones. Nielsen had predicted that milestone would be reached by the end of this year and it may still happen with a big holiday season ahead.