Arsenal's negotiations for Sporting's Viktor Gyokeres have stalled over a difference in overall value and terms.
The Premier League club's stance is to offer €65m, with potential performance-related add-ons of €5m and €10m.
That takes the overall value of Arsenal's package to €80m, but Sporting's hard line is that they want €70m guaranteed, with no add-ons.
The situation mirrors Arsenal's earlier pursuit of Leipzig's Benjamin Sesko in how neither club are budging. Those talks have temporarily paused over a difference of €10m.
There is a significant difference with the pursuit of Sesko, however. The desire of the Gyokeres camp to leave has created tension and made it much more difficult for Sporting to keep him.
Club president Frederico Varandas has been irritated by how the situation has been conducted - if not necessarily by the player himself - especially since Sporting have let it be known they won't stand in his way.
The 27-year-old's deep to go to Arsenal is now dependent on a breakthrough in talks.
You can sign up to DAZN to watch every Club World Cup game for free