Manchester United's part-owner, Sir Jim Ratcliffe, is unwilling to pay more than the £65 million valuation set by Brentford for the 25-year-old Cameroon international.
Despite Mbeumo expressing his desire to join Manchester United, talks between the two clubs have been at a standstill for several weeks.
Manchester United had previously made two offers for Mbeumo, but both were rejected by Brentford.
Recently, the asking price for Mbeumo has increased to £70 million, which has further complicated the negotiations.
Manchester United's financial situation is a major factor in the stalled transfer. The club needs to sell some of its players before making new signings, as it is currently struggling to make progress in the transfer window.
Players such as Marcus Rashford, Alejandro Garnacho, Jadon Sancho, and Antony are expected to leave Manchester United, but the club has yet to receive any concrete offers for them.
