The 33-year-old has already agreed terms on a two-year contract, with another 12 months available based on performances.
Aubameyang’s move to Stamford Bridge has been complicated by an armed burglary at his home near Barcelona, where he suffered a minor jaw fracture while trying to defend his family.
That injury could see him sidelined for over three weeks, which has led Chelsea to ask for a reduced price just before the 11pm BST deadline on Thursday night.
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Barcelona have yet to agree on a fee but all parties remain confident of completing a deal. Chelsea have a host of alternative targets available, having been priced out of a move for Everton’s Anthony Gordon and seeing Crystal Palace snub interest in Wilfried Zaha.
AC Milan forward Rafael Leao remains another option but a bid of over £100m would be needed to secure the Portuguese forward.
Thomas Tuchel has increasingly pressed to sign a midfielder, with a £40m bid for Edson Alvarez having been put in by the new Boehly-Clearlake ownership group.
Ajax are reluctant to sell yet another major talent after losing Antony and Lisandro Martinez to Manchester United, Sebastien Haller to Borussia Dortmund and Ryan Gravenberch to Bayern Munich already this summer.
However, the Mexico international has asked for the move and is pushing for an exit. Chelsea have also shown an interest in PSV Eindhoven defensive midfielder Ibrahim Sangare, but that deal seems even harder to do at this stage.
There are a host of exits planned at Stamford Bridge, with Billy Gilmour in talks with Brighton over a permanent move.
Ethan Ampadu has agreed on a loan switch to Italian side Spezia, with Joe Haigh having also left to join Derby on loan.
Academy centre-back Xavier Mbuyamba has joined FC Volendam in the Netherlands on a permanent deal and Bryan Fiabema has been recalled from his spell at Rosenborg to go out on loan in the EFL.