Fring, the mobile communications and social networking aggregator, says that VoIP provider Skype is blocking all interconnectivity between the two services. But Skype says it’s not to blame.

According to a press release from fring, it is “being forced to stop its four years of Skype interconnectivity following threat of legal action.”

The news comes just days after fring announced that a new version of its iPhone app had been approved at the App Store. The new app allows users to make video calls over 3G, something the Skype iPhone app still lacks. Fring calls the move by Skype “anti-competitive ambush.”

Fring went so far as to call Skype “cowards” in a blog post on the company’s website:

“They are afraid of open mobile communication. Cowards.

Needless to say, we are very disappointed that Skype, who once championed the cause of openness, is now trying to muzzle competition, even at the expense of its own users.

We’re sorry for the inconvenience Skype has caused you.”

Skype says fring is the one causing the inconvenience.

An official statement from Skype said that “Skype is disappointed that an amicable resolution was not possible but Fring’s decision to withdraw Skype functionality immediately was of its own choice.” The statement goes on to say that Skype encourages developers to build products that work with Skype APIs but that it will “rigorously protect its brand and reputation and those companies that do not comply with our terms will be subject to enforcement.”

Skype and fring do compete in the same market, as both companies offer VoIP, IM and video calling services. Skype recently released a new iPhone app that will bring changes to the service come the end of the year. While Skype-to-Skype calling will remain free, users will be asked to pay if they want to make Skype calls to cell phones or landlines over 3G using the iPhone app. Pricing details for this feature are yet to be announced, as price testing is ongoing.