​Atletico Madrid forward Antoine Griezmann will have to pay compensation if he does not opt to join Barcelona next summer, according to ​Sport.

The two clubs have reportedly agreed a "secret pact", detailing the conditions of a proposed transfer and the consequences if it is to fall through.

Should a deal fail to be concluded, Griezmann will be forced to pay compensation to Barcelona, and Barcelona will likewise be required to pay a sum to the player.

The terms of the 26-year-old's potential contract have been agreed, but a transfer fee has not yet been negotiated.

The Blaugrana are attempting to avoid paying Griezmann's full €100m release clause, although ​Atletico are reluctant to accept a reduced fee.

Sport claim, however, that the deal is all but done regardless of any difficulties in negotiation.

Espanyol v Atletico Madrid - La Liga

Barcelona are reportedly already considering when to unveil the signing of Griezmann, which is likely to be after this summer's World Cup finals in Russia.

The former ​Real Sociedad man had previously been strongly linked with a move to ​Manchester United, but the Red Devils' imminent acquisition of Alexis Sanchez means that they are expected to end their interest.

(You may also be interested in ​FanView: Sanchez Arrival Is Final Nail in Coffin for Man Utd Interest in Antoine Griezmann)

Griezmann will, instead, move to ​Barcelona, if Sport's report is to be believed, where he will join an already formidable attack consisting of Lionel Messi, Luis Suarez, Ousmane Dembele and Philippe Coutinho.