Borussia Dortmund boss Hans-Joachim Watzke on Saturday urged Bundesliga rivals Bayern Munich to come clean if they are interested in signing Poland striker Robert Lewandowski.
A fortnight ago Der Spiegel magazine reported Lewandowski, who has a Dortmund contract until 2014, had agreed to join Bayern, while on Friday TV channel Sport1 and Munich newspaper Muenchener Merkur said the transfer will go through for next season.
Sources claim the transfer, reported to be worth between 25 to 30 million euros, is set to be announced after Bayern's German Cup quarter-final at home to holders Dortmund on February 27.
With rumours rife, Borussia chief executive officer Watzke has told Bayern's senior figures to make their interest known.
"Scenario One: Bayern Munich has no interest in Robert - then this is all rubbish," Watzke told German Sky after their 3-0 win over Eintracht Frankfurt.
"Scenario Two: They are interested, then they will eventually have to show their cards, come to us and ask a question.
"If they do, they will get an answer, which will surprise them, maybe."
Lewandowski has scored 14 goals in 20 league games this season and his 30-goal haul last season was a major factor in Borussia winning the league and cup double.
After Friday's 2-0 win over Wolfsburg kept them 15 points clear of second-placed Dortmund in the Bundesliga, Bayern's bosses were tight-lipped on the Lewandowski topic.
"I just smile these rumours away", said Bayern chairman Karl-Heinz Rummenigge.
When asked if he could shed some light on the subject, he just replied drily: "That would take all the suspense out of it."
Coach Jupp Heynckes was also coy when asked about the growing rumours.
"Every week at Bayern, the latest show pony is paraded and linked to the club. It has always been the same since I have been here," said Heynckes.
"We don't allow such reports to drive us crazy. The players aren't impressed by it, on the contrary, they are often demotivated by it."
But with three strikers already in Bayern's squad with Croatia's Mario Mandzukic keeping Germany's Mario Gomez and Peru's Claudio Pizarro on Munich's bench, the rumour mill is clearly taking its toll.
"The club must commit themselves clearly and tell us what's going on," Gomez has said on the subject.