Only seven months after acquiring striker Pierre-Emerick Aubameyang on a free transfer, Barcelona has demanded £21 million from Chelsea.
Chelsea held discussions with the LaLiga giants over the weekend and is poised to make a bid this week.
As part of negotiations to move in the opposite direction, the Barcelona target Marcos Alonso has been mentioned.
The ex-Arsenal star has scored 11 goals in 13 starts since joining the Catalan giants in January but has now fallen down the pecking order following the signing of Polish striker Robert Lewandowski.
The Blues are chasing down Aubameyang to help them in attack after Romelu Lukaku re-joined Inter Milan on loan and Timo Werner sealed a return to RB Leipzig for £25million.
Boss Thomas Tuchel is keen to link back up with the 33-year-old forward after their positive relationship at Borussia Dortmund and would like to add a proven goal-scorer to his Chelsea ranks.