Chief Financial Officer Marcus Kuhnert told analysts at a capital markets day on Thursday that Merck still believed the range was possible "but it's damn challenging".

Shares in Merck fell 1.1 percent, among the biggest fallers on the Dax <.GDAXI>.

Merck slightly reduced its sales guidance range in August but maintained its target for adjusted core profit of between 4.4 and 4.6 billion euros(4.05 billion pounds).

At that time, Kuhenert had already warned that the target wouldn't be a "walk in the park".

(Reporting by Patricia Weiss; Writing by Victoria Bryan; Editing by Douglas Busvine)