BioWare has revealed the first official details for Mass Effect 3's multiplayer, which will take the form of 4-player co-op missions playable via Xbox Live, where players can choose from a variety of classes and races to form an elite Special Forces squad to fight together and "liberate key territories from enemy control."

Your progress in multiplayer will also have a direct impact upon the outcome of the single-player campaign, although BioWare is keen to stress that you can still achieve the "optimal, complete ending" in Mass Effect 3 through just playing the single-player portion of the game.

Also revealed is the Mass Effect 3: Galaxy at War system, which as a bonus to the campaign, enables players to manage their war against the Reapers using multiple methods, including 4-player co-op. You'll be able to build Shepard and his team's 'Galactic Readiness', gathering people, resources, weapons, armies and fleets through a variety of platforms and interfaces, the details of which are under wraps for now. We imagine social networking will probably play a part though.

There'll be character progression, weapon upgrading and leveling up in 4-player co-op too, as mentioned in a series of FAQs regarding the newly announced co-op mode posted on the BioWare forums, which also addresses a multitude of concerns, including whether co-op will have any kind of a negative impact upon the single-player campaign.

"We have always maintained that we would only add multiplayer into the Mass Effect series if it made sense and did not compromise the power of the single player campaign. Fighting together against a common threat was the multiplayer experience that made the most sense for Mass Effect 3. The way we have designed co-op as a way to take control of key conflict zones in the galaxy is a natural extension of the premise of Mass Effect 3," reads the FAQ post. "Our priority and focus with Mass Effect 3 has and always will be to deliver a complete and satisfying single player experience."

Ane here's the final word on why multiplayer won't affect the single-player campaign in Mass Effect 3: "BioWare is dedicated and focused on delivering an engaging, fun, and action-packed experience for Mass Effect 3, one that lives up the BioWare standard. To reach that level of quality, last year BioWare opened a studio in Montreal that is home to designers, programmers, engineers, and other developers. Both studios work together as partners, lead by the core Mass Effect team, unified in a single vision. Under the direction of Casey Hudson and other team veterans, both studios make contributions to both the single player and multiplayer modes in Mass Effect 3. Rest assured that no compromises were made to either of these modes in the development of Mass Effect 3."

So there you have it. Mass Effect 3, with it's 4-player co-op and Galaxy at War system, will be winging its way into stores on March 6th, 2012.