Moving to expand the sales potential of its Nexus One mobile phone, Google on Tuesday added a version of the Nexus One that works with AT&T's 3G network in the U.S. and with Rogers Wireless in Canada to its online store .

Introduced in January for T-Mobile's network, Google's Nexus One "Super Phone" hasn't broken or even bent any sales records. The Nexus One has sold about 135,000 units in the past 74 days, according to Flurry, a mobile analytics company.

That's about eight times less than the number of Verizon Droid or Apple iPhone device sold during the initial 74 day sales periods of those devices, respectively.

"As Google and Apple continue to battle for the mobile marketplace, Google Nexus One may go down as a grand, failed experiment or one that ultimately helped Google learn something that will prove important in years to come," writes Flurry VP of marketing Peter Farago in a blog post.

Farago argues that for Google to catch up with Apple in terms of developer support, it needs to increase the installed base of Android devices at a faster rate.

Google, however, says it's happy with its online phone selling experiment. "We're pleased with our sales volumes and with how well the Nexus One has been received by our customers," said a company spokesperson in an e-mailed statement. "The Nexus One is one of a fast growing number of Android handsets which have been brought to market through the open Android ecosystem. Our partners are shipping more than 60,000 Android handsets each day compared with 30,000 just three months ago."

Unlike the $179 Nexus One for T-Mobile, the AT&T-compatible Nexus One is not available under a two-year subsidized contract. It costs $529 unlocked, a price point unlikely to make it fly off the shelves.

Google's online store should offer more carrier options soon. In January, Google said to expect Android phones from Verizon in the U.S. and from Vodafone in Europe in its Web store come springtime, with additional partners at some point thereafter.