Google Voice provides users with a single phone number that routes calls to multiple phones. But making a call using that number requires initiating the call through Google Voice's Web interface rather than through a mobile handset. Google Voice then rings the caller and the person called and connects the two parties.

On Wednesday, Google plans to change that dynamic by allowing users to make Google Voice calls directly from their mobile phones. The company plans to release two mobile applications to make that possible, one that runs on Blackberry phones and one that runs on Android phones.

Vincent Paquet, product manager for Google Voice, said that Google is working with Apple on an iPhone app for Google Voice. It isn't ready yet.

The Google Voice app will allow users to use their mobile phones to access their inbox, place calls and send SMS messages with their Google Voice number, and make low-rate international calls.

When sending SMS messages in this manner, users don't have to pay SMS charges levied by their mobile carriers because the SMS messages are sent by Google.

The experience of using Google Voice through one of these mobile apps is much more seamless, said Paquet.

The Google Voice apps will allow users to set whether all calls, only international calls, or no calls get routed through Google Voice.

The Android app will be available for free from the Android Market and the Blackberry app will be available for download from Google's Web site.

Google launched Google Voice in March as a private beta test. Last month, it began sending invitations out to new users who had submitted a request to try the service. Paquet said that the reaction to the service has been pretty enthusiastic and that more people had requested invitations than anyone expected.

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