Brazilian mining mammoth Vale SA (VALE) said Friday that, because of the superior option of organically growing its own fertilizer assets, it hasn't made any proposal on acquiring companies in the sector.

The statement was a reaction to a Brazilian press report earlier this week that Vale was looking at further acquisitions of potassium assets.

Citing market sources, the Estado newspaper said Vale was targeting Mosaic Co. (MOS), which is controlled by Cargill Inc. and IMC Global Inc. (IGL).

However, Vale's statement wasn't enough to damp speculation over the company's intentions regarding Mosaic.

Estado said Vale's statement didn't specifically confirm or deny it was looking at acquiring Mosaic. It just said it was "frequently" sought out by financial intermediaries to consider opportunities for acquisitions in the fertilizer sector, Estado said.

Mosaic is valued at $25 billion, Estado added, and the company is the world's largest phosphates producer and one of the world's largest potassium miners.

Earlier this year, Vale paid $857 million for potassium-mining assets in Argentina and Canada.

In its statement, Vale said the fertilizer projects it is already developing would make it one of the world's largest producers of potassium, with output of more than 12 million metric tons a year.

Vale also has assets under development in Peru, Mozambique and northeast Brazil.

These assets are likely to render greater returns than those "offered by possible investment in acquisitions in this industry," Vale said.

Vale shares were flat on Brazil's Sao Paulo Stock Exchange on Friday, closing at 30.08 Brazilian reals ($15.58), where the shares opened. Shares of Mosaic closed down 0.84% at $49.56.

-By John Kolodziejski, Dow Jones Newswires; 55-21-2586-6086; John.Kolodziejski@dowjones.com