Forest are currently holding their pre-season training camp in Portugal and hope to reach an agreement while the squad remains in the country.

The 22-year-old has developed a reputation as one of Europe’s most talented young defenders and is already a key player for the Ivory Coast national team.

He was part of the team that reached the World Cup round of 32, although he only featured in their 2-0 win over Curacao in the final group stage game.

Diomande struggled with a muscle injury that kept him out for half of Sporting’s games last season. He featured just 17 times in the league but racked up 31 appearances across all competitions.

Despite struggling with injury problems, Diomande still helped Sporting to keep six clean sheets, while averaging 4.4 ball recoveries and 3.5 clearances per game.

Sporting reportedly value the defender between £30m and £35m, but negotiations between the two clubs are moving in a positive direction.

Diomande is already familiar with Forest midfielder Ibrahim Sangare through the national team.

While talks continue over Diomande, Forest are also on the verge of adding another important signing, with the club working on a deal for Xaver Schlager.

The Austrian midfielder is expected to arrive at the club’s Algarve training base to complete a medical before signing a two-year contract.

The 28-year-old will join as a free agent after leaving RB Leipzig, giving Forest an experienced option in midfield without paying a transfer fee.

Forest are also interested in Tottenham Hotspur midfielder Lucas Bergvall as they continue to explore further additions to Oliver Glasner’s squad.