By Sarah Sloat 

FRANKFURT--German salt and fertilizer company K+S AG on Thursday rejected a takeover approach worth EUR7.85 billion ($8.75 billion) by rival Potash Corp. of Saskatchewan, saying the proposal undervalued the company.

"The proposed transaction does not reflect the fundamental value of K+S

and is not in the best interest of the company," K+S said in a statement.

K+S was widely expected to rebuff the offer from Potash, which offered EUR41 a share.

The German company, which is developing a mine in the Canadian province of Saskatchewan, said the offer undervalues its products and projects. Potash also hasn't demonstrated a firm commitment to its employees' interests, K+S said.

A spokesman for Potash declined to comment.

Write to Sarah Sloat at sarah.sloat@wsj.com

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