SAN FRANCISCO (AP) - Google Inc. is adding a free email feature that may persuade more people to cut the cords on their landline phones.

The service unveiled last Wednesday enables US users of Google's Gmail service to make calls from microphone-equipped computers to telephones virtually anywhere in the world.

All calls in the US and Canada will be free through at least the end of the year. That undercuts the most popular PC-to-phone service, Skype, which charges 1.2 cents to 2.1 cents per minute for US calls. It also threatens to overshadow another free PC-to-phone calling service called MagicTalk that was just introduced by VocalTec Communications Ltd.

Skype, Google and many other services have been offering free computer-to-computer calling for years.

Google hopes to make money on its PC-to-phone service by charging two cents or more per minute for international calls. The international rates will vary widely, sometimes even within the same country. Google posted a rate chart at https://www.google.com/voice/b/0/rates.

People also will be able to receive calls on their PC if they obtain a free phone number from Google or already have one.

The phone numbers and technology for the new PC-calling service are being provided by Google Voice, a telecommunications hub that the company has been trying to expand. It had been an invitation-only service until two months ago when Google Voice began accepting all number requests.

Google disclosed last year that it had assigned about 1.4 million phone numbers through its Voice service, which can field calls made to a person's home, mobile or office number. Craig Walker, a Google product manager who helped develop Voice, said the service has expanded its reach since then, but he wouldn't provide specifics.

Besides planting Voice's technology into Gmail, Google also plans to promote the service by setting up red phone booths at universities and airports scattered across the United States.