The Spain international will have his medical on Merseyside on Friday and PA news agency understands he will complete the formalities on a four-year deal, for an initial $A35.6 fee, later in the day.

"I have made the most difficult decision of my sports career," said the midfielder in a video posted on Twitter.

"I will close this chapter on this wonderful club where I have grown as a player for seven years. Triumphs, joy and also hard times.

"But what I am most proud of is that I arrived in Munich as a young man filled with dreams and now I will leave completely fulfilled with a club, a history and a culture.

"Here I learned to love a tradition that I am now saying goodbye to, but which I will never forget.

"I have experienced fantastic moments: in this city ... with my Bavarian family who treated me so well and loved me every second.

"My decision is purely of a sporting nature. As a soccer player I want new challenges to develop myself further."

Australian Associated Press