"With titles from legendary designer Sid Meier and 2K's world renowned developer, Firaxis Games, 2K is one of today's foremost publishers," said Gabe Newell, co-founder and president of Valve. "Through this initial agreement with 2K, Steam's game library expands to include four great strategy games. We look forward to delivering more from 2K in the future."

2K develops and publishes front line PC, console and handheld entertainment software, with a strong presence in strategy, sports and high profile licensed titles. Steam is the only full-featured broadband platform for the delivery and management of games and digital content, and has pioneered its broadband services to over 10 million customers with core and casual games from today's leading publishers and developers.

"We are excited to add Valve to our roster of partners in the digital distribution area," said Paul Crockett, Strategic Sales and Licensing, 2K. "Being included in their vast network will assist us in expanding the reach of our products to a much larger audience."

PC versions of Sid Meier's Civilization IV®, Sid Meier's Civilization III®, Shattered Union and Sid Meier's Pirates!® will be available later this week via Steam. Details regarding future 2K titles available via Steam will be announced at a later date.