Liverpool boss Jurgen Klopp stressed his club had done everything possible to persuade Coutinho to remain at Anfield, but revealed the player had been “desperate” to move to Spain ever since July.
“It is with great reluctance that we – as a team and club – prepare to say farewell to a good friend, a wonderful person and a fantastic player in Philippe Coutinho,” Klopp said on Liverpool’s website.
“It is no secret that Philippe has wanted this move to happen since July, when Barcelona first made their interest known.
“Philippe was insistent with me, the owners and even his team-mates this was a move he was desperate to make happen.
“Despite that, we managed to keep the player here beyond the summer window, hoping that we would be able to persuade him to stay and be part of what we are looking to do.
“The player now has permission to complete the usual formalities to conclude the transfer immediately.”
Barcelona made Coutinho their top target after his countryman Neymar made a world-record £200.6million move to Paris St Germain in August and he will sign a five-and-a-half-year contract.