Diamond giant De Beers may withhold diamonds from the market in the fourth quarter depending on demand, a top executive said on Monday.%%De Beers is 45 percent owned by mining group Anglo American Plc, 40 percent by the Oppenheimer family and 15 percent by the Botswana government.%%An official informed that it would be difficult to ensure that sales in the second half of 2006 matched sales in the same period the previous year.%%De Beers said in July higher interest rates, rising fuel prices and geopolitical instability would make it tough for second-half sales to match those of a year earlier.$$The company expects the sluggish rough diamond market to pick up next year but gave no further details.