Managing director Gary Ralfe said demand for diamond jewellery needed to rise by about 6% in this half to absorb the 8 1/2% increase in sales of rough gems recorded by De Beers in the past six months, taking the total to $2.8bn (£1.8bn). But Ralfe acknowledged this was a 'stretch target' and represented a big jump on the 1% rise reported for the first half as fears of a double-dip recession took hold in the US.