A key obstacle in talks with Chelsea is the differing valuations of Garnacho and Jackson, while United are holding firm on their player valuations, including Antony.
United are also interested in Aston Villa's Ollie Watkins as a proven Premier League goalscorer and Emi Martinez as a goalkeeper.
Further targets include Benjamin Sesko, though his €80m asking price is high, and midfielders Morten Hjulmand and Joao Palhinha for the number six role.