The two clubs have been battling to sign the France international this summer but Chelsea appeared to have taken a decisive step forward at the end of the week, agreeing a fee worth around £55million.
Barcelona president Joan Laporta was even filmed telling a supporter that Kounde would be joining Chelsea, with a phone call from Thomas Tuchel apparently convincing the defender.
But the Catalan club never gave up on signing the 23-year-old and have been speaking to their Sevilla counterparts throughout the night and into the morning.
According to reliable Spanish journalist Gerard Romero on his Jijantes FC Twitch channel, on Saturday morning Barcelona reached an agreement in principle to sign Kounde.
Sevilla initially did not believe Barca would be able to match or even come close to Chelsea’s £55m offer, but they have now verbally agreed terms after the Blaugrana activated another financial ‘lever’.
Barcelona always felt the Frenchman preferred a move to Camp Nou over Stamford Bridge – though he was not prepared to refuse a move to Chelsea as Raphinha did earlier this summer.
Despite Chelsea appearing to be on the verge of signing Kounde, Barca refused to give up until the paperwork was submitted and the deal was official.
Director of football Mateu Alemany spent Friday night and Saturday morning in intense negotiations with Sevilla and Barca now believe they have won the race to sign the centre-back.
Romero also claims that Barca winger Ousmane Dembele played a key role, phoning up his international team-mate and encouraging him to move to Camp Nou.
Chelsea had been extremely confident of signing Kounde, with personal terms agreed since last summer when they first tried to sign him, and Tuchel appeared to be in a buoyant mood on Friday as he spoke to the media.
Asked about Kounde, he replied with a big smile on his face: ‘No news. If there will ever be news about Jules Kounde I will tell you.’
When it was suggested Kounde had snubbed Barca, Tuchel again had a wide grin and replied: ‘That’s what you say, but I will not start commenting on other players.’
If Barcelona have managed to gazump Chelsea it would be nothing short of a disaster for the Blues, while it would also be the second time this summer they have had their transfer plans torpedoed by the Catalan side.