Spain's midfield hero Xabi Alonso said Friday that moving from Real Madrid to Bayern Munich had been "the most complicated" decision of his career.

Alonso spoke about his "new adventure" after Real confirmed that it had reached agreement with the German champions for a transfer that Spanish media said was worth 10 million euros ($13 million).

The 32-year-old passed a medical in Munich on Thursday.

A member of the Spanish side that won the World Cup in 2010 and the European Championships in 2008 and 2012, Alonso joined Real from Liverpool in 2009.

He announced his retirement from international football on Wednesday, one of many Spanish stars to stand down after the country's World Cup debacle. But the recent purchase of German midfielder Toni Kroos had also complicated his future with Real, despite his role in the club's 10th European Cup and Champions League triumph last season.

Alonso told a press conference that the transfer decision had been "the most complicated of my life."

"After winning the 'Decima' (10th title), I sensed a new cycle opening at the club and that I should do the same," he said.

"Perhaps many things ended and that to stay at my best level I needed this change."

"Thanks for everything. That's all," Alonso added on his Twitter account after the press conference.

Alonso, who played 114 games for Spain, had been tipped to move last year, but in January signed a contract extension with Real until 2016.

His experience, midfield vision and brilliant long passes will be a valuable boost to Bayern's Spanish coach Pep Guardiola who has serious midfield troubles.

Javi Martinez, Bastian Schweinsteiger, Rafinha and Thiago Alcantara are all sidelined with injuries.

Alonso started his career at Real Sociedad before moving to Liverpool in 2004.