Challenger Magnus Carlsen closed in on the crown after defeating defending champion Viswanathan Anand in the ninth game of the World Chess Championship match here on Thursday.
On what turned out be a dramatic affair, Anand missed out on his chances in white pieces and suffered a painful defeat that almost sealed the fate of the match.
Carlsen now leads 6-3 and needs just half a point from the remaining three games to become the new world champion.
It was a Nimzo Indian defense that Carlsen chose as black and Anand, realising well that this was his last chance for a strike, went for the Saemisch variation.
Anand had used this system before, in World Championship match against Kramnik and later in a gem of a match against Wang Hao of China.
Carlsen showed some signs of nervousness in the early stages of the middle game after he went for a line that is not favoured in top level chess.
Anand got his chances by way of a King-side attack while Carlsen pushed harder on the other flank. The position in the middle game looked very dangerous for Carlsen but with precise calculations, he kept himself in the game.
Even till the end of the game, Carlsen's queen and one Bishop remained on the initial squares as mere spectators to the proceedings, while he defended his position with all available resources.
On the 22nd move, Anand had about 25 minutes more than Carlsen and optically dominating position, but the Norwegian world number one had calculated that his King was guarded against any checkmate threats.
On the 23rd move, Anand spent nearly 40 minutes and decided to continue the attack instead of equalising once again. This was more to do with match situation as Anand had things under control but another drawn result would not have improved the match situation.
Carlsen found the best possible moves from this point and Anand simply blundered on his 28th move by moving his knight to a check coming from a new promoted queen. Another move would have helped continue the game but this was certainly not Anand's day.
With just a draw needed, Carlsen should be able to take home the title in the 10th game itself when he gets white pieces.
"We got a very sharp position from the opening, basically I missed something with the pawn rollers, it was really a very tough game," Carlsen said after the game.
The Norwegian added that he was trying to calculate as best as possible.
"I was trying my best and I could not find a forced win for white," he said.
Anand said he had not seen the blunder. "I just got a little excited and played this knight move. I realised immediately what I had done," the Indian said.