Verizon Wireless said on Tuesday it will sell two mobile phones with Google Inc's Android operating system this year, part of a partnership that could boost Google's efforts to challenge Apple Inc in the fast-growing smartphone market.

In a conference call on Tuesday, Verizon Wireless CEO Lowell McAdam said the partnership could result in the introduction of multiple co-developed Internet connected devices per year going forward.

The first Android phones from Verizon Wireless, a venture of Verizon Communications Inc and Vodafone Group Plc, will support the Google Voice software application which allows consumers to make low-priced international calls and which Apple has yet to approve for its iPhone.

Google has said that Apple rejected Google Voice, while Apple contends it is still evaluating the software, in a high-profile spat that has attracted the attention of the U.S. Federal Communications Commission.

You either have an open device or not. This will be open and we expect to bring that application to market when we bring the first device out, McAdam said regarding Google Voice.

The Verizon partnership represents an important source of support to Google's efforts to gain a foothold in the smartphone market and caps a string of Android phone announcements including Motorola Inc's recent introduction of the Cliq phone and HTC's Hero phone, slated for release in the U.S. next week.

Andy Rubin, Google's top Android executive, said there were currently nine Android phone models available from various makers, with Verizon Wireless bringing an additional two to market this year. Google has previously said it expects between 15 and 20 Android powered devices to be available by year end.

Google views mobile phones as an important way to extend the growth of its online advertising business, as people around the world increasingly access the Internet from smartphones.

Analysts believe that mobile phone ads have the potential to be more lucrative than Internet ads viewed on PCs, given the that mobile ads can take advantage of an individual's physical location to better target a marketing pitch.

Google CEO Eric Schmidt said on Tuesday that there are currently more than 10,000 software applications that run on Android phones.

By contrast, Apple announced recently that there are more than 85,000 apps available for the more than 50 million iPhone and iPod touch devices that it has sold.

Google and Verizon Wireless said the forthcoming phones would be co-developed by the two companies, though executives said Google's role in terms of the hardware development was primarily in identifying optimal designs from manufacturers.

Our view is this a family of devices, it's not just a smartphone or PDA, McAdam said on the call.

And while Eric and I certainly have in our minds that we'll have multiple devices per year, we don't really have a hard target at this point, he said.

(Additional reporting by Franklin Paul; Editing by Derek Caney and Tim Dobbyn)