Bayern Munich coach Jupp Heynckes has rejected advice from German legend Franz Beckenbauer to ring Pep Guardiola and glean some tips for its Champions League semi-final against Barcelona.

"I don't understand how a former player and coach can say that," said Heynckes ahead of Bayern's German Cup semifinal against Wolfsburg on Tuesday, with his team bidding to become the first German side to win the treble.

"Maybe I should ring Johan Cruyff, after all he instigated the Barcelona system," he said.

Bayern hosts Barcelona at Munich's Allianz Arena in the semifinal, first leg on Tuesday April 23, but Heynckes has repeatedly insisted he will not be speaking to ex-Barca coach Guardiola, who will succeed him as Munich coach in July.

Last Friday, Heynckes angrily refuted a German reporter's question on the subject by saying: "Have a little respect for me and my work. I have never consulted anyone for advice".

After Beckenbauer told German daily Bild that Heynckes "shouldn't be too proud" to contact Guardiola, the Bayern coach said he did not want to put the Spaniard in the awkward position of revealing his former employers' secrets.

"(Bayern) have a very good scouting department. I know Barcelona very well and we wouldn't be doing Pep Guardiola any favors," said Heynckes.

"He would respect his former employers and wouldn't give any secrets away. That's an unwritten rule."

Jurgen Klopp, coach of Bayern's Bundesliga rival Borussia Dortmund, which faces Real Madrid in the European semi-finals, was blunt when asked if he thought Munich's senior figures, including director Matthias Sammer, would ask Guardiola for tips.

"I would bet my backside that Mr Sammer and Mr Guardiola will be telephoning each other," quipped the Dortmund coach, who whipped up a debate in the German media over the weekend by admitting he had had a hair transplant.

Bayern chairman Karl-Heinz Rummenigge used Klopp's coiffure confession to fire back.

"Perhaps he should have bet his hair, he could have a transplant for that. His backside would be much more difficult," he said.