It's a whole new ball game. Or it could be if fans gathering for RoboCup 2001 get their way.

The artificial intelligence (AI) fraternity's annual football tournament kicks off this Saturday (4 August). By pushing back the boundaries of robotics, AI pioneers hope to make super automatons that could carry off the soccer World Cup by 2050.

After IBM's Deep Blue computer beat Gary Kasparov at chess in 1997, the AI community turned to a more challenging sport. Soccer simulates the real world more closely than the static turn-taking in chess, explains AI researcher Peter Stone of AT&T Labs-Research in New Jersey. "It's the next step up in a lot of dimensions," he says.

Successful robot soccer sides have to see the ball, work as a team, learn, and make continuous decisions on the changing state of play and the opposition's strategy. The annual RoboCup tournament sees the robotic best battling it out in the name of AI research.

Competition will be hot at the 2001 tournament in Seattle - 120 teams from 25 countries are expected to play before a broadcast audience of three million. "It's the most popular AI competition," says Stone, offering a range of leagues that test different aspects of robot design on the field. Once the whistle has blown, no human intervention is allowed - robots must rely on their programmed talent.

With a string of wins under his belt, Stone is a seasoned coach in the pocket-sized robot league. Here, five-a-side, 15-centimetre robots wage war on a pitch the size of a ping-pong table. Speed and ball skills are key: last year's winners walked it with an impressive backspin roller bar that let robo-players turn and dribble, explains Stone.

Mid-sized 50-cm robots, playing on a 9x5 metre field offer "a more challenging league", that last year went to penalties.

The 'simulator' league is more like a computer game: 11 versions of one team's software battle 11 of another's on screen. The most focused on AI, this league is the only one in which rules such as offside apply. Last year's winners, from Portugal, took tips from the coaches of real Portuguese team FC Porto.

Champion in '98 and '99, Stone is entering an experimental simulator side this year, in which players have differing abilities. "Some are faster, better kickers or have more stamina," he says. Preliminary results suggest that putting stronger players in defence is a winning strategy. But, as in the human version, "Any team can win on the day," says Stone.

Representing Britain, Huosheng Hu of Essex University in Colchester is entering the Sony legged league: three-a-side reprogrammed Sony robotic dogs. Hu hopes his Essex Rovers will improve on a disastrous performance in 2000 when they went out in the first round.

A good perception system is key to a hot-shot soccer dog, he explains. "If robots can't find the ball, they can't function." To help them, the ball is orange, goals yellow and blue, and the teams sport magenta or pale blue strip. Hu hopes to score with his advanced colour depiction algorithm that adjusts to different lighting conditions. "I hope we can get in the top 10 - maybe the top 5," he says.

Although team designers are reluctant to reveal their strategies beforehand, all research will be published after the finals on 9 and 10 August. By focusing on a complex task, RoboCup is a test bed for basic technical issues, such as perception, coordination and learning, which must be solved to advance the field. "If we want to use AI in the real world we have to deal with these difficult problems," says Hu.

Search and rescue robot teams that patrol earthquake disaster zones will be demonstrated

The results have widespread applications, adds Bob Bishop, chief executive of computing company SGI. "In future, robots can do things we don't want to do ourselves," he says. Search and rescue robot teams, for instance, that patrol earthquake disaster zones will be demonstrated at the games.

And AI enthusiasts are optimistic that the robo equivalent of Zinedine Zidane could one day win the World Cup. "It could get up to human level," Bishop enthuses. And, in the warm up to world domination, the robot tournament is "a thriller to watch", he adds.