The Atletico Madrid striker has agreed personal terms and Chelsea have met the buy-out clause in the striker's contract. The only delay has been because of the hamstring injury suffered by the Spain international at the end of the season.

But he is back in training with his country and yesterday passed a medical in Barcelona.

Chelsea boss Jose Mourinho has said he is looking for a striker that can "open the gate" after missing out on the Premier League title last season in part because of a lack of goals.

Samuel Eto'o, Fernando Torres and Demba Ba scored just 19 in the league between them.

Costa, 25, scored 27 goals in 34 league starts for Atletico plus eight in the club's run to the Champions League final.