Volkswagen said it had not presented Porsche with an ultimatum to accept its layout for a merger of the two carmakers, denying a media report and accusations from Porsche.
"There is no ultimatum," a VW spokesman told Reuters on Sunday. He would not comment further.
Porsche on Saturday accused VW and its key shareholder Lower Saxony of extortion following a magazine report that VW and the regional state had demanded Porsche accept a tie-up of the two carmakers with VW in charge.
Der Spiegel magazine reported in its online edition on Saturday that Porsche had been pressed to agree by the end of June that VW take a 49% stake in Porsche's sports car business or else face claims to pay back a €700 million ($983.8 million) loan in September.
Porsche Chairman Wolfgang Porsche and his deputy on the supervisory board, Uwe Hueck, said in a statement on Saturday they had been given an ultimatum by VW and Lower Saxony and that they would "not accept extortion."