In a new survey of prospective U.S. buyers, RIM and Microsoft drift, Nokia disappears

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The launch of the Verizon VZ iPhone has not visibly slowed the triumphant march of Google’s GOOG Android operating system through the mobile heartland of America, according to a Nielsen Wire report released Tuesday.

In monthly surveys conducted from January to March 2011 — on either side of the Feb. 10 Verizon launch — 31% of U.S. respondents planning to buy a new smartphone in the next year said they wanted an Android, up from 26% six months earlier.

Only 30% said they wanted an iPhone, down from 33%. Research in Motion RIMM , Microsoft MSFT , Palm HPQ and Other also lost ground. Americans who plan to buy Nokia NOK smartphones were lost in the round-off error.

If there is any comfort for Apple AAPL in the results it is that Not Sure grew to 20% from 18%. That and the fact that Apple sold $10.45 billion worth of iPhones last quarter, overtaking Nokia — the world’s largest manufacturer of mobile phones — for the first time.

It’s not clear how much additional ad revenue Android generates for Google, but it couldn’t be that much.

Below: Nielsen’s pie charts of market share of recent buyers and total installed base.

Covers period from October 2010 to March 2011

Covers period from October 2010 to March 2011

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