Talks are understood to have reached an impasse after Sporting refused to budge from their £68 million (€80m) valuation, which is a huge increase on the £39 million (€45m) fee United and Tottenham were quoted for the midfielder in the summer.
United have now walked away from the table and no further discussions are planned for this weekend between the two clubs.
Sky Sports News are reporting that Red Devils officials, usually led by executive vice-chairman Ed Woodward in such matters, feel their latest bid of £43 million-plus £17 million in potential add-ons is about right for the in-form Sporting star.
Reports that Fernandes, who has grabbed 13 goals in 21 games in all club competitions this season, could be at Anfield to watch United in action against Liverpool were clearly premature.