Diomande was linked with both Arsenal and City in January before he completed a £6.5m move to Sporting from Danish side Midtjylland.
The 19-year-old has impressed in Lisbon and earned his first Ivory Coast cap this month amid talk of a new contract, which would maintain a rumoured £71m release clause.
Luis Cassiano Neves, the player’s agent, has stated that negotiations are not advanced over a renewal but Diomande is nonetheless committed to Sporting.
“[Diomande] is extremely satisfied at Sporting,” he told A Bola.
“He is very focused on the club and their objectives for this season, which include winning the league title. And he knows that Sporting is the ideal club for this evolution.
“He will be happy to sit at the table with Sporting but so far there is nothing [to discuss]. Sporting is Diomande's present and future, he wants to evolve but there is nothing regarding [a contract] renewal.”