The 22-year-old, currently with Ivory Coast at the World Cup, has been made aware of Leeds' interest, though his focus for now remains entirely on the tournament being played across Canada, Mexico and the United States.
Leeds United are considering an offer worth around €40m, with a further €10m in potential add-ons, for a player Sporting are adamant is not for sale. The English club have already approached Diomande's camp to gauge his thinking, with a formal proposal to Sporting expected to follow.
Sporting's stance is firm. The Lisbon club want to keep Diomande for at least one more season, having extended his contract in January through to 2030 with a release clause set at €80m.
Sporting signed Diomande from Midtjylland in 2023 for an initial €7.5m, having previously loaned him to Mafra in Portugal's second tier. Performance-related clauses tied to appearances saw that fee rise to €12.5m over time, and the club later paid Midtjylland a further €2m to reduce the Danish club's sell-on percentage on any future transfer from 20% to 10%.
In total, Sporting's investment in Diomande now stands at around €14.5m, a deal that has comfortably paid off given the level of interest, particularly from England, that the defender now commands.
Diomande, who is working his way back to full fitness after a thigh injury, is still waiting for his World Cup debut.
Leeds' willingness to offer a fee in the region of €50m for a defender who has not yet established himself as an automatic starter for his country reflects the scale of ambition behind the club's recruitment plans this summer.
Sporting's resistance, backed by a release clause well above what Leeds are currently offering, suggests any deal would require a significant escalation in the English club's proposal before negotiations could move forward in earnest.