The 24-year-old, who is currently with the Germany squad at the World Cup, has been heavily linked with a move to the Santiago Bernabeu in the past few weeks.
Despite recently refusing to confirm whether he had agreed to join the Spanish giants, Kroos has now hinted that his future could lie with Madrid.
"I've made a decision and can't say," he told TZ Munich. "I read things. It's not hard to find out, but I'm saying there is nothing done.
"First I want to play the World Cup and when finished my decision will be known. I'll say it myself. Before then there is nothing. There's one week of the World Cup left and then we'll know more."
Kroos and his Germany teammates return to action on Tuesday when they face hosts Brazil in the World Cup semi-finals.