The Portuguese midfielder remains in talks over a switch to Old Trafford, but the deal has been held up due to Sporting’s demands.
United are still hopeful of landing Fernandes this month, but refuse to pay Sporting’s £68million asking price.
Fernandes failed to secure a move away from Sporting in the summer after interested clubs were priced out of a move.
Sky Sports report the 25-year-old is now putting pressure on the Sporting board to lower their demands and strike a deal with United.
Both clubs are continuing to negotiate, and are working to come to a conclusion.
United fear that paying over the odds for Fernandes could cause a hike in transfer fees when it comes to doing business at the end of the season.
Tottenham were the closest to signing him in the summer but would not offer more than £38.5m for his services, despite Fernandes agreeing a move to north London.
He has since signed a new contract with Sporting, though the club’s manager Silas has backed him to be a Premier League star.
Speaking at the time of penning his new deal in November, Fernandes said: “You [Sporting fans] can expect more and better. I promise the same delivery and dedication so we can have more moments of glory as we had last season.”
Fernandes is yet to agree terms with United, but rumours in the Portuguese press are believed to have been circulated as a method to force their hand to get the deal over the line.
Sky Sports’ pundit Paul Merson has urged United to turn their backs on signing the Sporting star however, and make a move for Aston Villa’s Jack Grealish.
“Forget Bruno Fernandes – Manchester United should be trying to sign Jack Grealish,” Merson told the Star,
“He is one of the top ten players in the Premier League right now. He is absolutely different class and would walk into almost any other Premier League team.
“Bruno Fernandes is a full international. He’s had clubs all over Europe looking at him. But he’s never played in this league before. Grealish has. And he’s ripping it up every week.”