Blizzard has doubled to 20,000 the number of US beta testers working on WarCraft III: The Frozen Throne.

Blizzard said: "We are pleased with the results and feedback that the beta test is generating and would like to offer the opportunity for even more players to experience all the new features the game has to offer."

The company is selecting new beta testers from among the 100,000 users who applied to join the original test. Selected users will receive an email from Blizzard "in the next few days". Blizzard has also posted feedback from testers.

Warcraft III: The Frozen Throne offers a new sequence of adventures set after the events of the previous title. These include new Heroes for each race, new spells, abilities, units and areas to explore. The title introduces 'Neutral' mercenary Heroes for hire as players battle through levels. The world editor is also improved: players are able to create unique cut scenes and voiceovers. New multiplayer maps will also appear. Players must conquer new enemies to save the world from the forces of darkness once again.

The expansion set is scheduled to ship in summer 2003 and will cost $35. No UK price is available yet.