Fletcher is widely expected to turn down United’s offer of a new contract, meaning he would become a free agent at the start of next month.
Leeds are then hoping to swoop to make him their player on a permanent basis.
However, the Whites do have a back up plan should Fletcher decide to stay with United.
Reports have already suggested that Leeds will be willing to pay Fletcher up to £7,000-a-week in wages, and they would also welcome the 20-year-old to join on a temporary move.
Garry Monk has made Fletcher one of his main targets since taking over at Leeds, as he looks to upgrade the his new side’s strike force.
Leeds are also currently working on a deal to bring Marcus Antonsson to Elland Road, with the Swedish striker expected to complete a move to the Yorkshire side in the near future.