Bayern Munich attacker Thomas Muller is keen to join Louis van Gaal at Manchester United.
The Daily Mail says Bayern Munich are growing agitated at their forward's demands for re-assurances.
An official approach was made by United two weeks ago for the 24-year-old.
Van Gaal gave Muller his chance at Bayern when there were calls for new players to be brought in and that has not been forgotten by the player despite his affiliation with his boyhood club.
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