Google is taking on Skype with its new computer-to-phone calling service. (Paul Sakuma/Associated Press)

Google has launched a service that lets Gmail users make free calls from their computers to phones, with the service available to Americans and Canadians.

The voice service allows Gmail users to call landline or cellphone numbers from a Gmail account accessed on a computer. Google said calls to the United States and Canada will be free for at least the rest of the year, with calls to other countries offered at "very low rates," such as two cents a minute to countries including the United Kingdom, France, Germany, China and Japan.

"Given that most of us don’t spend all day in front of our computers, we thought, 'wouldn’t it be nice if you could call people directly on their phones?'" wrote software engineer Robin Schriebman on the Google blog. "Starting today, you can call any phone right from Gmail."

The company said the service will initially be available only to Americans, but Google Canada spokesperson Wendy Bairos Rozeluk said Canadians can access it by changing their Gmail settings to "English-US."

The service is different from Google Voice, which lets smartphone users make free phone calls over a wireless data connection, she said, and the existing computer-to-computer Google Chat feature. Users of Google Voice, which is only available in the U.S., receive their own phone number, which will be displayed as the outbound caller ID when using the new service.

Since Google Voice is not yet available in Canada, this feature won't be usable by Canadians. Bairos Rozeluk said there was no timeline on when Google Voice might become available in Canada.

Canadians, however, will still be able to make international calls by setting up a payment account with Google Services, which bills to the user's credit card.

Gmail users will see a new "call phone" option added to their chat list over the next few days as the service is rolled out, the company said. Users will have to install a voice-and-video plug-in to take advantage of the service.

Google's new voice service is a direct competitor to Skype, which offers various types of internet-based calling services. Skype offers free computer-to-computer calling, as well as paid services that allow users to call landlines and cellphones. Skype is partly owned by the Canada Pension Plan Investment Board.

Both services are prevented from offering Canadians incoming calls by the Canadian Radio-television and Telecommunications Commission. CRTC rules require all phone providers to include enhanced 911, which enables emergency operators to automatically locate callers.

Google's service will also put pressure on competing web email services from Yahoo and Microsoft. Neither company immediately replied to requests for comment.