Man and computer in chess cliff-hanger

Kramnik, 27, offered a draw after his 28th move on Thursday at the tournament at Manama in the Gulf state of Bahrain.

Deep Fritz, a German-developed computer, can evaluate 3.5 million moves per second. But Kramnik was allowed to practise against it for two weeks before the contest.

The match is a sequel to the 1997 contest in which Deep Blue, an IBM computer, defeated then world champion Garry Kasparov.

Lost advantage

If he wins Saturday's decider, Kramnik will get $1m, while a draw will earn him $700,000 and a defeat $500,000.

Kramnik's aggressive tactics initially confounded the computer, but the machine's handlers have helped it cope with this playing style.

The Russian was crowned chess world champion in 2000 when he beat Kasparov, his former tutor, in London.

"To be honest, the result will, to a large extent, be based on luck. It depends on so many factors, even the way that I sleep," Kramnik said.

"The computer doesn't feel any pressure at all, and therefore has a real psychological advantage - I need to think really deeply about what I will do in the final game."

But Mathias Feist, one of Deep Fritz's creators, insisted that "humans will always have more attacking opportunities".

Analysts said Kramnik might have conceded defeat too soon in the sixth game on Tuesday when there was still a possibility of a draw.

During early games, Kramnik found a way to exploit the playing style of the computer and frustrated its ability to look ahead and predict which way a match was going.

Although the first bout in the eight-game series was drawn, Kramnik won games two and three comfortably.

Deep Fritz was created using standard hardware by the German company Chess Base.