"I want to stress that it is, and never has been, about money," Ballack said.

"I am not 23 or 24, have a great contract at Bayern and my family and I are comfortable in Munich. I just want a new challenge."

Chelsea look to be that new challenge but their Portuguese manager Jose Mourinho has demanded Ballack make a swift decision after holding talks with the player.

"He has to have made a decision before the World Cup," Mourinho said in an interview with Bild am Sonntag.

"For me Ballack is one of the best players in the world," enthused Mourinho. "He has everything and his intelligence on the pitch impresses me. I also like him as a person."

Ballack is said to be stalling as he seeks reassurances over a first team spot in Chelsea's star-studded side but will make a decision before the World Cup begins on June 9.

"I will make a decision before the World Cup," explained Ballack. "But my personal situation is not important. What is important is winning the league and cup double."