Commodities trader and mining group Glencore Xstrata is said to have reached a preliminary deal in Mauritania for a 1bn-dollar contract to access railway and port facilities as it expands into iron ore.According to the Financial Times, Glencore has agreed with state-controlled miner Société Nationale Industrielle et Minière (SMIN) over a price to use its railways.This is thought to be the first of three major obstacles standing in the way of the construction of the Askaf mine.The FT said that Glencore is also near a deal with a construction contractor, its second barrier, but is still in talks with the government about tax issues. The paper, citing people familiar with the matter, said that the tax discussions could take months.Askaf is one of three big projects that Glencore is hoping to develop in Mauritania, two of which are in partnership with SMIN. Askaf is a standalone development for the company, however.The stock was down 0.1% at 312.8p by 10:50.BC