Networking specialist Cisco has decided to mount a challenge on Microsoft's takeover of Skype, lodging an appeal before the European Commission earlier this week.

According to the Associated Press (AP), Cisco has expressly declared that it does not intend to block the merger, which cost Microsoft $US8.5 billion and approved by both the United States and European regulators in October last year.

"Cisco does not oppose the merger, but believes the European Commission should have placed conditions that would ensure greater standards-based interoperability," Cisco video conferencing chief Marthin De Beer was reported by AP saying in a blog post.

That specific condition is for Microsoft to allow inter-connectivity between video calling services, which is currently dominated by Skype with its reported active users of some 170 million all over the world.

Skype's video call service has also been recently made available through Facebook's social networking site, which in turn counts more than 750 million users.

Cisco is mostly engaged in providing networking equipments but its video conferencing service has started picking up and with the prospects of wide corporate subscriptions, the business division has become a lucrative market for major players.

Cisco has expressed serious concerns that once Microsoft has assumed full ownership of Skype, it will impose exclusivity on video calls within the Skype network and block inter-connectivity.

There exists a tendency for Microsoft to "seek to control the future of video communications, De Beer wrote in his blog.

"Making a video-to-video call should be as easy as dialling a phone number ... Today, however, you can't make seamless video calls from one platform to another, much to the frustration of consumers and business users alike," De Beer said.

On its filing, Cisco asked EU's General Court to review the Commission's decision on the Microsoft-Skype merger and consider the possibility of amending the original ruling and allow the inclusion of a provision that will require Microsoft to guarantee open standards for video calls and conferencing.

A spokesman, however, for the Commission told AP that EU's earlier decision will be defended before the Court.

Also, Microsoft said in a statement that it is confident that the earlier EU ruling will be sustained by its General Court.

"The European Commission conducted a thorough investigation of the acquisition, in which Cisco actively participated, and approved the deal in a 36-page decision without any conditions," the software giant was quoted by AP as saying in a statement.