The Gunners have tabled an offer worth a total of 80 million euros - comprising a 65-million-euro guaranteed fee, along with 5 million and 10 million in performance-related add-ons.
However, Sporting are holding firm, insisting on a straight 70 million guaranteed payment with no add-ons, leading to the current impasse.
This transfer saga echoes Arsenal's earlier pursuit of RB Leipzig's Benjamin Sesko, which also faltered over a 10 million discrepancy in valuation.
However, the Gyokeres case carries added urgency due to the player's own desire to leave. The 27-year-old forward is keen to make the move to north London, adding pressure on Sporting to strike a deal.
Inside the Portuguese club, tensions are reportedly rising. Sporting president Frederico Varandas is said to be irritated by how the negotiations have been managed, although his frustration does not appear to be directed at Gyokeres himself.
Despite the firm stance on the transfer fee, Sporting have privately indicated that they will not block the move outright.
Sporting CP president Frederico Varandas has confirmed that striker Viktor Gyokeres will face internal disciplinary action after failing to report for pre-season training on Saturday.
In what could mark the beginning of a reshuffle in North London, Arsenal are reportedly prepared to offload Belgian forward Leandro Trossard, with Turkish giants Fenerbahce emerging as the likely destination.
Arsenal have secured the signing of Denmark international Christian Norgaard from Brentford, bolstering their midfield with a proven Premier League talent.
Arsenal have signed Brentford captain Christian Norgaard for 10 million pounds, with add-ons potentially taking the deal to 12 million pounds, per David Ornstein.
