Mr Reithofer went on to say that no cost savings could possibly be great enough to warrant ruining the core of a brand.
"There are clear limits. The BMW brand, which one study has valued at $24 billion, must not be diluted or the brand identity damaged," Mr Reithofer said.
The comments come one week after Daimler CEO Dieter Zetsche pushed for a broader alliance with BMW saying there were in principle only a few areas where a cooperation was out of the question.
BMW last year examined the possibility of building the next-generation Mini on an Alfa Romeo platform but scrapped the idea after concluding that the outcome would not look or drive enough like a Mini to be worth the risk.
Mr Reithofer nevertheless said that BMW continued talks with Daimler to see where they could cooperate for the sake of scale and added that he would be willing to strengthen ties with its French engine partner, PSA/Peugeot-Citroen.
"When the new Peugeot chief is in office, we will also discuss whether one can expand the existing cooperation," Mr Reithofer said.
The Quandt family that controls nearly a majority of BMW is said to be keen not to see its influence diminish at the company it rescued decades ago from a planned takeover by Daimler-Benz.