Vietto, 26, joined Sporting from Atletico Madrid in May 2019 for €7.5m and the Leões will not sell him at a loss.
Sporting will reportedly consider a sale if Al Hilal improve their offer for the Argentine to €11m.
The Lisbon club only have 50% of Vietto’s pass, with his former club Atletico in line to receive half of any transfer fee.
Vietto scored eight goals in 35 games in his first season at Sporting. This season so far, he has yet to find the net in four appearances.
Before joining Sporting, Vietto had spent time on loan at Sevilla, Valencia and Fulham.