Barcelona are preparing a bid for Alex Song but are unwilling to meet Arsenal’s £15 million valuation of the midfielder.The Spanish giants have upped their interest in the Cameroon international after being encouraged by their exploratory enquiries for the 24-year-old.Song, who joined Arsenal, initially on loan, in 2005, is flattered by Barcelona’s interest and keen to hear what they have to say.Arsene Wenger is reluctant to sell the only senior defensive midfielder in his squad even though Song has developed the creative side of his game over the last two seasons.Arsenal are in talks with Real Madrid over a season-long loan for Nuri Sahin, but the midfielder is regarded by Wenger as more of a deep-lying playmaker who can stand in for the injured Jack Wilshere rather than a protector of the defence.He has three years to run on his current contract and Wenger might conclude that it is the right time to cash in on him.