Concluding the trilogy's narrative journey, Mass Effect 3 sees the earth's political powers convinced of the threat that Shepard witnessed in the first two games.

The third game sees that ancient, technologically advanced fleet of Reapers launch an attack on Earth, marking the start of a galaxy-wide purge of all sentient life.

Shooting for a March 6 release date in North America (March 9 in European regions), Mass Effect 3 was originally due towards the end of 2011.

The delay enabled its developers to make sure the action-roleplaying hybrid would appeal to as many people as possible, said the CEO of publisher Electronic Arts.

It also meant that potentially sticky clashes with role-playing game Skyrim and action titles Gears of War 3, Uncharted 3, Modern Warfare 3 and EA's own Battlefield 3 could be avoided.