Verizon Wireless will let its customers make free or low-cost calls using Skype on its smart phones, making it the first U.S. operator to allow the Internet phone company on its network.

Verizon customers will be able to use the Internet telephony service on nine different smartphone models starting next month, Verizon and Skype said at the Mobile World Congress in Barcelona on Tuesday.

The companies said they had created a Skype mobile offering for 3G smart phones allowing users to make unlimited Skype-to-Skype calls on the U.S. carrier's network as well as international calls on Skype calling rates.