Verizon Wireless, the largest US mobile operator, and Skype, the biggest VoIP provider, are jointly developing an application that will enable the operator’s 3G smartphone users to make free or cheap international calls, the two companies announced last night.

The application – Skype mobile – will be available for download by users of popular Verizon Wireless smartphones from next month. The application has been jointly developed by the two companies to run on the Verizon Wireless 3G EV-DO network.

The alliance confirms a change of attitude among mobile operators who have historically been hostile towards VoIP providers. Another sign of how mindsets are altering in the mobile industry was O2’s recent acquisition of VoIP provider Jajah.

John Stratton, Verizon Wireless’s chief marketing officer, explained where the US operator hoped to gain additional revenues from the new alliance: “We are looking at opportunities to improve our share of international minutes by attracting users with family overseas or expatriates [living in the States].” 

Stratton would not confirm how many smartphone users will be capable of receiving Skype’s service. Verizon Wireless’s total user base is over 90 million and its smartphone base runs into the millions. 

Domestic US calls will also be possible through the new service but Verizon Wireless is pushing the international aspect. As with the Skype service elsewhere, calls between Skype users will be free while Skype Out calls (to non-Skype users) competitively priced.

The Skype mobile application will be offered to users of Verizon Wireless smartphones including various BlackBerry models such as the Storm, Curve and Tour, as well as HTC’s Droid Eris, Motorola’s Droid and the latter’s forthcoming Devour handset.

Interestingly, Verizon’s CTO Dick Lynch was asked at a press conference Monday whether he would consider using Skype as a voice solution when it launches LTE this year. The issue of enabling voice over LTE is a thorny topic, although the industry (including Verizon) appears to be uniting behind IMS as the preferred technology solution (in an initiative known as Voice over LTE, or VoLTE). Lynch didn’t want to completely rule out the option of Skype as an interim solution for LTE voice services, though said that the company’s current plans are to use its existing, hugely successful EV-DO network for voice during the early stage of LTE launch, whilst the IMS (VoLTE) solution is being developed. “I don’t see that we have an interim problem,” he added. “We will move to Voice over LTE [VoLTE] a lot more quickly than any of us think.”