The Red Devils' latest offer of £55million is still on the table, however they're reluctant to go much higher for the Chelsea star.
The latest bid was their third formal offer for the 24-year-old, however that was turned down on Friday evening.
United insisted that the offer would be their final bid, with the club still confident of landing the England star.
However the Red Devils are reluctant to put all of their eggs in one basket, with Caicedo among those being targeted as an alternative.
The Brighton star has been heavily linked with a move to both Chelsea and Arsenal in recent months, with United now pursuing a deal of their own.
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A deal won't come cheap though, with the Seagulls believing that Caicedo is worth as much as Declan Rice.
West Ham have valued their skipper at £100million amid interest from Arsenal and Manchester City, a figure that Brighton believe is suitable for their own midfield star.
With such figures being quoted, Man United's pursuit of Mount is unlikely to be over.
The 24-year-old has just 12 months remaining on his contract at Stamford Bridge.
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But Chelsea are keen to get their full worth for the academy graduate.