Fantasy strategy game Dota 2 won't ship until 2012, Valve boss Gabe Newell has revealed.

Valve plans to launch an invitation beta after the Gamescom tournament ends. After that a public beta will launch. "And then we'll probably start worrying about how we'll monetise it," Newell told Eurogamer.

"We'll just go into progressively wider and wider distribution. I don't think it'll be shipped until next year."

Dota 2 was penned for launch this year.

"But then," Newell continued, "with a game like this, you just keep shipping. You add new heroes. You try out new game modes. You are constantly tweaking item and hero balance. It's very much an ongoing thing."

Dota 2 is the sequel to Warcraft 3 mod Defense of the Ancients, and is being developed by the reclusive IceFrog, one of a number of of modders who helped make Dota what it is.

While Dota 2 will be distributed through Valve's own platform, Steam, the firm is yet to decide on a business model.

"We don't have a plan," Newell said. "IceFrog has a bunch of testers he's worked with as long as he's been doing development. The first thing we've been working with is addressing their concerns. We've been through four or five different versions of the user interface, getting it to the point where we've addressed the feedback we've got from those guys.

"For us now, this tournament is a really good step. A bunch of the features we're building in the design of Dota 2 related to being able to put on a tournament like this. There's a bunch of stat stuff. There's a bunch of website development, support for simultaneous, four-language broadcasting.

"This was the next step."

Could Dota 2 end up going free-to-play, like Team Fortress 2? "We don't know. We don't have plans yet," Newell said. "The problem isn't to figure out what your monetisation strategy is. If you have something with a super careful monetisation strategy and it sucks, it doesn't matter.

"The most important thing is to do something that resonates well with the existing Dota players and creates a vehicle for new players to join into the community. That's the hard problem. That's the interesting one to solve."