Four objective-based co-operative missions will be introduced as a free download on Xbox Live, PlayStation Network and Steam.
The missions will introduce new environments and characters, and will take place prior to the events of the single-player campaign.
Designed to emphasise teamwork, players will face waves of new enemies and once again do battle with the elements.
Announced in 2009, Spec Ops: The Line sees players control Captain Walker, a US Delta Force soldier on a mission to rescue his squad.
2K has said it will feature the darker realities of war, putting players in difficult situations where the line between right and wrong becomes blurred.
Lead game designer Cory Davis subsequently told Digital Spy that the game shares similarities with Bioshock.
The game is available now in North America, releasing later this week in Europe.
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Watch a trailer for Spec Ops: The Line below: