PARIS, France — Christian Dior is set to announce after its couture show in early July that Maria Grazia Chiuri is joining the French fashion house from Italy's Valentino, two people familiar with the matter said.Chiuri will be taking on one of the most important jobs at Dior. She will also be the first woman creative director in the company's 70-year history, following in the footsteps of celebrity designers including Yves Saint Laurent, Gianfranco Ferre and John Galliano."I understand that it will be announced after the (July) couture show," one of the sources said.Dior was not immediately available for comment.Chiuri will join Dior at a difficult time. The brand's fashion sales growth has dropped in the past year and a half, going from double-digit to flat sales growth in the first quarter of this year.Dior has attributed its poor results to the luxury market slowdown but some fashion industry experts have suggested it might be facing some desirability issues.Dior is the parent company of LVMH, the luxury industry's biggest luxury group. It generates around €5 billion in annual sales, of which more than three fifths come from perfume and cosmetics. It has been struggling to find a replacement for Belgian designer Raf Simons who left unexpectedly in October.Chiuri has worked wonders at Valentino together with her design partner Pierpaolo Piccioli, acting as the brand's joint-creative director since Valentino Garavani, who hired them himself, announced his retirement in 2007.The pair won several prizes and helped to turn Valentino into one of the luxury industry's most profitable luxury brands and one of the strongest in terms of sales growth.Under their creative leadership, Valentino has become known for its light, graceful and highly romantic designs, applauded by fashion editors. Dior, which has been producing relatively modern styles, would benefit from a return to more romantic, fairytale-like aesthetics, some fashion critics have said, when asked about Chiuri on an unattributable basis.Mayhoola, the Qatari investment company that owns Valentino, this week acquired the French fashion label Balmain, another fast-growing brand, for around €460 million ($524 million), three sources told Reuters on Tuesday.By Astrid Wendlandt; editor: Jane Merriman.