Borussia Dortmund's fan department said on Thursday that it had raised concerns about the sponsorship deal with arms manufacturers and technology company Rheinmetall before it was finalised and announced.
A statement said that the fan department was informed in a monthly meeting with club leaders and asked for feedback, with the matter to be treated confidential.
"In a subsequent open dialogue with representatives of BVB's management, the fan representatives expressed general concerns about the explosive nature of the partnership and its communication, as well as doubts about its compatibility with Borussia Dortmund's values," the statement said.
"We value the established dialogue structures that enable the club and fans to regularly discuss even controversial topics with each other in a spirit of trust. It is not always possible to reach a consensus in these dialogues - as was the case in this instance."
Dortmund announced a three-year partnership with Rheinmetall on Wednesday, with club CEO Hans Joachim-Watzke naming security and defence "fundamental cornerstones of our democracy" and speaking of a "new normality."
The announcement drew sharp criticism but also support, while Mona Neubaur, minister for economic affairs in the state of North Rhine-Westphalia, where Dortmund and Rheinmetall are based, spoke of "mixed feelings."
She told dpa that companies like Rheinmetall are needed "to be able to defend our democracy and our freedom in an emergency. And yet the defence industry is not like any other industry. I can therefore understand that many fans have mixed feelings about the sponsorship."