Russian agriculture firm Phosagro plans to raise at least $500 million (350 million euros) in a public offering on the London and Moscow exchanges next month, the company said in a statement. The offering implies a company valuation of $4.8 billion to $6.1 billion, Phosagro said, putting it just behind Russia\'s second-biggest potash producer Silvinit. With the industry consolidating worldwide, Silvinit will next month merge with Russia\'s biggest producer Uralkali. Phosagro, whose chief Vladimir Litvinenko is a close ally of Prime Minister Vladimir Putin, has received permission to float up to 21.35 percent of its shares as Global Depository Receipts (GDRs) outside Russia. Late last year, Phosagro announced plans to make a rival bid for the world\'s biggest fertilizer maker Potash Corp to counter a hostile offer made at the time by mining giant BHP Billiton. That attempt failed, but the Uralkali alliance has been mentioned as a possible taker of a stake in the main potash producer of Belarus. The importance of potash fertilizer has grown over the last years owing to mounting demand for food in the world and rapidly-expanding China is a major importer of the product.