A national newspaper claimed on Wednesday that Derby had offered to make Commons their highest earner next season.
Manager Nigel Clough said: "Talks are ongoing. We do not want to get into figures on who is the highest-paid player but we are doing everything we can to try to keep Kris.
"There is only one sticking point in contract negotiations - money. Length of contract is not an issue for either of us. It is purely what we can afford and what Kris' ambitions are."
Commons has scored 10 goals in 18 Championship games this season and Clough added: "I think his performances this season have been more team-orientated than at any time we have seen him in the 22 months we have been here."