MUNICH (AFP) - Pep Guardiola has promised embattled Bayern Munich will put up a fight in Tuesday's Champions League semi-final, second-leg, in their near-impossible bid to deny Barcelona an eighth final appearance.

Bayern are chasing a miracle at the Allianz Arena after their humbling 3-0 first-leg defeat at the Camp Nou last Wednesday when Lionel Messi capped a dazzling display with two goals.

"We all know it's going to be a mammoth task but we're not going to give up," said forward Thomas Mueller.

Bayern believe they can claim a historic win with Germany captain Bastian Schweinsteiger suggesting: "Sometimes unbelievable things happen in football and we hope we're going to catch one of those days."

But their confidence has been dented by losing their last four games since winning the German league for the 25th time a fortnight ago and the losing streak is their longest since 1991.

In Saturday's latest defeat, Bayern crashed 1-0 at home to neighbours Augsburg and had to play 77 minutes with 10 men after reserve goalkeeper Pepe Reina was sent off.