The plan allows unlimited calls to land-line phones in 34 countries for US$9.95 (euro6.31) per month, said Don Albert, vice president and general manager for Skype North America.

The countries encompassed include most of Europe, plus Canada, Australia, New Zealand, Chile, China, Singapore, Taiwan, Japan, Korea and Malaysia.

Calls to domestic land lines and cellphones are included as well, as are calls to cellphones in Canada, China, Hong Kong and Singapore, but not cellphones in other countries.

Skype has already been selling unlimited calls to the U.S. and Canada for US$3 (euro1.90) a month. It is expanding that offering with another plan, for US$5.95 (euro3.77) per month, that gives free calls to Mexico City, Guadalajara and Monterrey, and a discount on calls to other places in Mexico.

Skype is generally used as a software application running on a computer equipped with a microphone and speakers or a headset. But subscribers will also have the option to call a local number from their phones and be connected to international numbers that fall under their plan, paying only local access charges or using their cellphone airtime.

Unlimited international calling plans have been popping up in recent years from hardware-based phone services like Vonage International Holdings Corp. and cable companies, but the prices are generally higher, and the plans are add-ons to basic calling plans that cost even more.

Skype said its subscribers called phones for 1.7 billion minutes in the first three months of the year, compared with 14.2 billion minutes used in computer-to-computer sessions, which are free.