Talks between the clubs have accelerated in the past 24 hours and are expected to continue throughout the week.
Mbeumo, 24, is understood to have already agreed personal terms with United on a deal reportedly worth around 250,000 pounds per week.
He has made it clear to Brentford that he favours a move to Old Trafford over a potential reunion with former boss Thomas Frank at Tottenham Hotspur.
While Spurs had shown strong interest in Mbeumo earlier in the window, their attention has now shifted to Crystal Palace star Eberechi Eze.
The 26-year-old attacking midfielder, formerly of Queens Park Rangers, has impressed with 40 goals and 28 assists in 127 appearances for Palace. He recently etched his name into club folklore by scoring the winner in the FA Cup final against Manchester City.
Eze's contract runs until 2027, but a 68 million pounds release clause was triggered at the end of the season, making a move increasingly plausible. Manchester City have previously expressed interest in the England international, but Spurs are now frontrunners.
Manchester United, keen to bounce back from a disappointing campaign, are flexing their financial muscle this summer.
The Red Devils have already secured the 62.5 million pounds signing of Matheus Cunha from Wolves and remain linked with further reinforcements, including Chelsea's Christopher Nkunku and Fiorentina's Moise Kean.
Manchester United and Chelsea are reportedly exploring blockbuster moves that could see Alejandro Garnacho and Christopher Nkunku switch clubs, as both players seek fresh starts after turbulent seasons.
Tottenham have completed the signing of highly rated Japan international centre-back Kota Takai from J-League side Kawasaki Frontale.
Manchester United winger Alejandro Garnacho has drawn attention during the off-season after posting a photo of himself on social media wearing an Aston Villa shirt.
Manchester United are reportedly exploring a move for Aston Villa's Emiliano Martinez as the summer transfer window intensifies.
