Internet phone service provider Skype plans to start charging US and Canadian users $29.95 (£15) per year for unlimited calls to regular phones in both countries, as the end of a free trial offer looms.

Users who sign up before January 31, 2007 will receive a special rate of $14.95 a year and 100 free minutes of international calling, Skype said. Any user wishing to continue using Skype to make calls to regular phones or mobile handsets after the free trial expires December 31, but does not want a yearly plan, can pay for SkypeOut at a rate of just 2.1 cents per minute for calls within the US and Canada.

Computer-to-computer calls using Skype software will remain free.

Skype allows users to make voice and video calls to regular landlines, mobile phones, or PCs over the internet. The company's popular software can also be used to share files, send instant messages, conduct conference calls and more.

The new plan to start charging users for calls to regular phones comes just six months after Skype launched a free trial of its Voip (voice over Internet protocol) service in both countries.

The strategy also pits Skype against other Internet calling carriers, such as Vonage, which offers a $24.99 monthly package in the US that includes calls to several European countries such as the UK, Spain and France, as well as extras such as voice mail, 911 emergency-dialling and a free phone adaptor.

Skype, a Luxembourg company bought by eBay last year, already serves more than 136 million registered users globally, as of the end of September 2006. The company made a name for itself by offering free PC-to-PC calls over the internet with the aid of its free software.