According to journalist Christopher Michel, the club are "seriously working" on a deal for the 25-year-old, who has been identified as an ideal long-term option.
The expected departure of Casemiro has accelerated the need for reinforcements, with United targeting a player capable of offering both immediate impact and longevity.
Currently at Newcastle United, Tonali remains a central figure, but the club could be forced into difficult decisions if they miss out on UEFA Champions League qualification.
A potential financial shortfall may open the door to a sale, although Newcastle are expected to demand a premium fee - particularly for a Premier League rival.
Tonali, formerly of AC Milan, is valued at approximately 69 million GBP by Transfermarkt.
The Italian international is widely regarded as a complete box-to-box midfielder, combining defensive intensity - through tackling, interceptions and pressing - with strong progressive passing and the ability to drive play forward and create chances.
United, however, are not alone in their interest. Arsenal are also monitoring the situation closely, setting up a potential transfer battle. Despite this, United may hold an advantage due to the promise of consistent game time.
Michael Carrick has praised the rapid rise of Kobbie Mainoo but delivered a clear warning ahead of Manchester United's trip to Bournemouth, insisting his side must stay grounded despite growing confidence.
Manchester United are standing firm on their decision to part ways with Casemiro at the end of the season, despite a surge in form that has sparked emotional pleas from supporters for the veteran midfielder to stay.
Leny Yoro hopes Casemiro and Harry Maguire both remain at Manchester United, as the club prepare for the likely exit of the Brazilian while continuing contract talks with the England defender.
Michael Carrick has highlighted Bruno Fernandes' importance to Manchester United as speculation over the midfielder's future grows ahead of the upcoming transfer window.
