Google is expanding and lowering the cost of its Google Voice phone calling service, giving people living outside the US the ability to make inexpensive local and international calls from within their email accounts.

Google's in-email calling service was first launched in the US last year. Since then Americans have been able to make free national calls and low-cost overseas calls to their friends and family via their Gmail accounts and smartphones.

US and Canadian users will continue to benefit from free calls within those countries "at least for the rest of 2011," said Google, while international users will be charged $0.01 per minute to make calls to the US and Canada.

The VoIP segment is becoming increasingly competitive. Internet calling services such as Vonage, Fring and iCall have harnessed pent-up demand for smartphone-based VoIP apps and market leader Skype recently teamed up with Facebook to offer free and cheap calls to people using the social network.

To entice people away from rival services, Google has reduced the cost of calls to 150 destinations around the world and eliminated call connection fees.

Google Voice call prices are relatively cheap - much less costly than sending a letter, quipped Google.

"For example, it's now only $0.10 (or €0.08) per minute to call mobile phones in the U.K., France or Germany (landlines are $0.02/min), $0.15/minute to call mobile phones in Mexico and $0.02/min to call any phone number in China and India," said Pierre Lebeau, Product Manager, Gmail Team.

The full list of call rates is available on the Google Voice rates page.

The service is now also available in 38 new languages. Calling credits can be purchased in euros, British pounds, Canadian dollars or US dollars.

"We're rolling out this feature over the next few days," said Lebeau, "so if it's available in your country you'll see a little green phone icon show up at the top of your chat list and you'll be ready to make calls (you'll need to install the voice and video plug-in if you haven't already)."