Anglo American agreed last year to take control of De Beers, buying out the Oppenheimerfamily, but the world's largest diamond producer by value has been a weak spot for the global miner, as a bumper 2011 was followed by a tougher 2012.
In the first half, profits halved and De Beers took the unusual step of allowing buyers of its rough diamonds - known as "sightholders" - to defer the purchase of as much as half of their gem allocation until March 2013.
"It was a pretty dull (first half). The general anticipation is for a slight improvement in the second half," CE Philippe Mellier said, as the diamond producer referred to a recovery in the fourth quarter, and stabilising prices.
"We are now entering the festive season... the big season for the selling of polished diamonds, and the outlook is slightly more positive than we thought. We are cautiously optimistic that the end of 2012 will be better than the beginning of 2012."
In its first major presentation to investors since the Anglo deal completed, De Beers said sales would be lower over the year. Its prices will be 12% weaker at the end of this year than at the end of 2011, and 10% lower on average.
"Whilst in the last couple of months we have seen slightly firmer sales, clearly these prevailing conditions for demand and price have put pressure on our second half sales," saidGareth Mostyn, De Beers' CFO.
The diamond producer said it had felt the impact of slower growth rates in China and softer US demand, while India - the world's largest cutting and polishing centre for diamonds - was hit by strikes, low consumer confidence and a weak rupee.
Mellier said he hoped the advent of a new leadership in China would help boost domestic consumption.
Production also remains weak, after De Beers increased maintenance and waste-clearing operations during the last year of softer prices, but was then also hit by a slope collapse at its Jwaneng operation in Botswana.
De Beers said on Friday it expected production of around 27-million carats, below 2011 and below forecasts of 28-million to 30-million carats given to the market in July. Increased production at its Venetia and Orapa mines would help offset the Jwaneng stoppage, Mostyn said.
De Beers, which once controlled as much as 70% of the rough diamond market, now has a share of just over a third by value. The group said on Friday it did not think that would be a "blanket prohibition" on further deals.
De Beers surprised many in the industry earlier this year when it confirmed it had considered - though later decided against - a bid for BHP Billiton's majority stake in the Ekati mine in Canada. It would have been only the diamond group's second deal in Canada, more than a decade after it took control of Snap Lake, its first mine outside Africa.
De Beers has sold off a number of its higher cost mines in recent years, but the group said Snap Lake, currently De Beers' highest cost mine, remained core to the group.
Edited by: Creamer Media Reporter