Arsenal have reached agreement in principle with Borussia Dortmund over the club-record €63m (£55.5m) signing of Pierre-Emerick Aubameyang, though the completion of the deal may yet hinge on rival clubs, including Chelsea, securing their own reinforcements as the January transfer window looks set for a frantic finale.

Negotiations have been ongoing for Aubameyang for a fortnight with Arsenal always confident a deal could be concluded after the player made clear his desire to move to London. The Gabon international has agreed a contract to 2021 believed to be worth around £180,000 a week, which would make him the highest-paid player at the Emirates Stadium.

Yet Dortmund will formally sanction the 28-year-old’s sale only once they have secured a replacement and, having been led to believe Olivier Giroud is not interested in a transfer to Germany and ruled out a move for Anthony Modeste of Tianjin Quanjian, they have turned their attentions to Michy Batshuayi.

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The under-used Chelsea striker, who has also interested Sevilla, scored twice for the champions against Newcastle on Sunday but has made only four Premier League starts under Antonio Conte since his £33.2m arrival from Marseille in the summer of 2016. The Belgian is keen to move to Dortmund, with talks continuing between the clubs. Chelsea had envisaged a loan but are in dialogue over the potential inclusion of an option to make the deal permanent in the summer. Chelsea are willing to let him leave, though only once they, too, have secured a striker to ease the workload on Álvaro Morata.

Talks have hit an impasse with the Roma forward Edin Dzeko, with Chelsea believed to be reluctant to offer a deal to 2021 for a player who turns 32 in March. The club have a policy not to commit significant transfer fees, or contracts longer than a year, to players in their 30s and are reluctant to break this to recruit the Bosnian.

Dzeko, for his part, is settled in Italy and in no hurry to leave a club to whom he is contracted until 2020. A weekend of talks with his agent failed to yield agreement and left Chelsea contemplating furthering their interest in Leicester City’s out-of-favour Islam Slimani or, more intriguingly, Giroud.

Arsène Wenger’s instinct has been to retain Giroud – who has also been the subject of tentative interest from West Ham – and certainly to reject the prospect of releasing him to a direct rival for a top-four place, but the 31-year-old has made only one Premier League start this season and is desperate to gain more regular playing time before the World Cup. Chelsea have held talks aimed at securing the forward, either on loan or for an initial £15m plus potential add-ons. That could suit Giroud, who has no great desire to move from London mid-season.

The resolution of such a complex chain of possible deals may hold the key to Arsenal breaking their transfer record for the second time in as many transfer windows, eclipsing the £52m purchase of Alexandre Lacazette. A club delegation – led by the chief executive, Ivan Gazidis, and including the head of recruitment, Sven Mislintat, and Huss Fahmy, who works on player contracts – spent time in Westphalia last week.

Reports in Germany suggest a deal was settled in principle over the weekend for a player who moved to Dortmund in 2013 and has proved prolific there, with 141 goals in 213 appearances, if controversial at times. Aubameyang had been championed by Mislintat, who was instrumental in securing him at Dortmund from the French club the French club Saint-Étienne.

Chelsea are to complete the signing of Roma’s left wing-back Emerson Palmieri for an initial £17m until 2022, with that deal to be confirmed regardless of their failure to agree a deal with Dzeko. Baba Rahman has moved to Schalke and Charly Musonda is to join Celtic, both on 18-month loans. “He’s a shining light in Chelsea’s academy,” said Celtic’s manager, Brendan Rodgers, of Musonda. “There were 24 other clubs interested in signing him.”