Arsenal's move for Pierre-Emerick Aubameyang is expected to go down to the wire as the Gunners wait on Borussia Dortmund landing a replacement before allowing the striker to leave.
The understanding is a deal has been agreed in principle between the two clubs - subject to Dortmund bringing in their own forward.
Arsenal have until 2300 on Wednesday to get the transfer over the line and it could be touch and go given all of the factors and logistics at play.
Reports have suggested the Premier League club will break their transfer record for the second time in just over six months following the arrival of France striker Alexandre Lacazette last summer.
Any move for Aubameyang is now dependent on Dortmund signing their own forward, with the Bundesliga transfer window open until February 2.
They have been strongly linked with a move for current Arsenal striker Olivier Giroud.
But the waters are muddied by Chelsea's apparent emerging interest in Giroud, 31, who turned down a summer move to Everton to fight for his place at the Emirates Stadium.
Since then he has started just one Premier League game and is now more open to a move - especially in a World Cup year.
Arsenal's stance on Giroud is similar to Dortmund's with Aubameyang, with manager Arsene Wenger saying on Friday that "if nobody comes in, nobody goes out.".
With Francis Coquelin and Theo Walcott already sold and Alexis Sanchez allowed to leave for Manchester United in a swap deal for Henrikh Mkhitaryan, it is clear why Wenger is reluctant to allow more talent to leave without first recruiting.
It is understood there has been no prospect raised of a similar exchange between Chelsea and Arsenal despite some reports that David Luiz could be offered for Giroud.
But if Chelsea can lure Giroud across the capital it could mean Dortmund switch their attention to Blues striker Michy Batshuayi.
The Belgium international has scored 10 goals this season but still seems to be unfancied by manager Antonio Conte - who has been linked with a whole host of attacking players throughout the January window.