The Germany defender is a top defensive target for Manchester United manager Louis van Gaal, with a new bid expected to be tabled this week.
However, Klopp has scoffed at the rumours, insisting: "What was it today? Mats to ManU? For how much? 20 million?
"For such sums you can just forget that straight away!"
United's pursuit of Hummels is expected to intensify when Van Gaal and United return from their tour of the US on Wednesday.
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