The 24-year-old Germany international sees his current contract expire next year and the Bavarian giants are desperate for him to commit his future to the club.
But those talks have stalled, with Bayern – who have recently seen David Alaba and Jerome Boateng sign contract extensions – still battling to secure the signature of Kroos.
"To be honest…because the talks so far have not led to a new contract…it's always about the money in every agreement," Rummenigge told Kicker.
"We are interested that Toni prolongs his contract."
Rummenigge also reiterated that Bayern are interested in extending Croatia striker Mario Mandzukic's contract.
That is despite the impending arrival of Poland forward Robert Lewandowski, who will join on a free transfer from Borussia Dortmund at the end of the season.
"He (Mario Mandzukic) is under contract until 2016. I have dropped hints to both him and his agent that we would be willing to hold talks," Rummenigge said.
"We are very pleased with him. There were quite a few people who shook their heads in disbelief when we signed him form Wolfsburg.
"But he was exactly the type of player we wanted. He has brought in those qualities, and we are very pleased."
