The Egyptian is emerging as a serious target for the Anfield club to replace Mohamed Salah.
As Salah enters the final months of his deal, Marmoush may be seen as the clear alternative.
However, the German club's sporting director Markus Krosche told German newspaper WELT it will only take a big fee to prize Marmoush away.
He said: “With many players who come to us, it is ultimately the case that we offer them an environment in which they can develop - knowing full well that we will let them go if they develop faster than the club itself.
“This is an agreement we make with the boys. That's why we are able to attract so many exciting players, because they know they can take the next step in Frankfurt.”
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