Manchester United's initial £45m bid for Brentford's Bryan Mbeumo, with a further £10m in add-ons, has been rejected.
Brentford values Mbeumo at over £60m and may extend his contract by an additional year to retain him.
Thomas Frank has acknowledged that Mbeumo's sale is possible but would be "expensive".
Mbeumo is attractive to United due to his Premier League experience, versatility across the forward line, and strong fitness record.
Manchester United aims to bolster their attacking options following the expected departures of Marcus Rashford, Jadon Sancho, Alejandro Garnacho and Antony and are also targeting a goalkeeper, wing-back, and midfielder.