Guimaraes, 28, currently earns £160,000 a week and has two years remaining on his contract at St James' Park. Arsenal have held talks with the Brazil midfielder's representatives and are reportedly planning a second approach after intermediaries were told any bid would be rebuffed. Newcastle United say they have had no direct contact from the Gunners.
The proposed new deal, which would run until 2030, would make Guimaraes the highest-paid player in the club's history. New contract talks have not yet begun, but Newcastle are understood to be open to tabling the offer as a statement of intent.
Toon sources are not surprised by the growing speculation, noting that similar talk surfaced three years ago when Guimaraes' agent was looking to secure an extended deal. On that occasion, the situation was resolved without a departure.
Arsenal and Manchester United are both monitoring developments, and Newcastle's own sources acknowledge that either club could potentially match or exceed any new contract offer — adding urgency to getting an agreement in place before the window develops further.
For Newcastle, Guimaraes is irreplaceable at the heart of their midfield and any sale would fundamentally alter their ambitions for the coming season. The club's intention to hold firm is clear, but the contract timeline will need resolving sooner rather than later.
Newcastle's strength of feeling over Guimaraes reflects how central he has been to everything the club has built under Eddie Howe. Losing him would not just weaken the squad — it would send a signal about the club's ability to retain elite players in the face of sustained pressure from the top of the Premier League. That is a message they have no interest in sending.