Berlin, Apr 12 (IANS): Defending champions Borussia Dortmund took a huge step towards retaining their Bundesliga title with a 1-0 victory over main rivals Bayern Munich.

Robert Lewandowski scored in the 77th minute and goalkeeper Roman Weidenfeller saved a penalty from Arjen Robben to leave Dortmund six points clear of Bayern with four games remaining in the season.

"Dortmund are 99 percent certain to be champions," Bayern chairman Karl-Heinz Rummenigge was quoted as saying by Xinhua.

More than 450,000 fans applied for tickets for Dortmund's likely title decider with Bayern, which had been billed by German media as "the game of games".

Dortmund had a nervous ending as keeper Weidenfeller missed the ball and brought Robben down in the penalty area in the 85th minute, giving Bayern the chance to level the match, but the Dortmund keeper guessed the right way to deny the Dutchman.

"I think in the last three years I've taken 10 or 11 penalties and converted them all," Robben said. "That's the first I missed, and at such a time. It's bitter."

Elsewhere, third-place Schalke were unable to take advantage of Bayern's loss by slumping to a 1-4 defeat at Nuremberg and Hannover beat Wolfsburg 2-0 in a battle to qualify for Europe.