Atletico Madrid forward Sergio Aguero has asked the Spanish club to release him from his contract.
The 22-year-old Argentine international extended his deal to 2014 in January but his buy-out clause was reduced from £52m to £40m.
"After five intense years a stage in my personal development has ended and I have to move on to a new one," said Aguero on his website.
Chelsea, Liverpool, Manchester City and Tottenham have been linked to Aguero.
"I said long ago that when I wanted to go, I would say so publicly," added the Atletico striker. "And the time has come.
"So I keep to my word and here I am. I find it hard to leave Atletico. It hurts and saddens me."
Aguero has scored over 100 goals for Atletico since joining from Independiente as a teenager in 2006.