German salt and fertilizer company K+S AG once again rejected Potash Corp of Saskatchewan's takeover offer on Friday, saying the Canadian company's assurances about maintaining jobs and mine sites in Germany were unreliable.

Saskatoon, Saskatchewan-based Potash Corp sent an unsolicited letter to K+S's management and supervisory boards, K+S said in a statement. The letter included a proposal for a "business combination agreement" based on an unchanged price of 41 euros ($44.82) per share.

The price is too low, and Potash Corp's commitments on maintaining jobs and keeping mining sites open in Germany are not enforceable, K+S said.

Potash Corp, the world's second-largest potash miner, wants to acquire No. 5 producer K+S as global competition ramps up among sellers. K+S has suggested Potash plans to shrink the company.

A Potash Corp representative confirmed the company sent a "private letter" to K+S's boards, but would not comment further.

Shares of Potash Corp eased in New York and Toronto, while K+S stock climbed 1.4 percent in Frankfurt.

Potash Corp has been pushing to talk with K+S management despite the German company's initial rejection last month of the Canadian company's 7.9 billion-euro ($8.6 billion) bid of 41 euros per share.

Analysts have speculated Potash wants to acquire K+S, a higher-cost producer, to shut some production to support prices.

People familiar with the situation told Reuters that Potash offered K+S a guarantee it would keep German mines operating for five years.

If it acquires K+S, Potash Corp would finish building the German company's Canadian mine and sell its potash offshore through Canpotex, Potash Chief Executive Jochen Tilk said on July 30.