BEIJING - Chinese movies must retain authenticity and creativity, even when they are Sino-foreign film co-productions, Oscar winning directors Oliver Stone and Alfonso Cuaron said on Thursday.

The two directors as well as French actor Jean Reno, Wanted director Timur Bekmambetov and Paramount Pictures chief operating officer Federick Huntsberry, were attending a forum on co-production, as part of the Beijing International Film Festival, which was launched on Wednesday.

Stone said money was an important factor behind cooperations, but the Platoon director also noted that China's involvement in Iron Man and the Transformers franchise was not good enough, and that such films needed more Chinese creative elements.

The director said China should not become like the United States or "some kind of international money-oriented film making machine".

While speaking about China, Cuaron said his storyline in Gravity that astronaut Ryan Stone escaped by taking refuge in Chinese space station Tiangong was not calculated to woo Chinese viewers.

He said China should not follow models but create its own, with diversity.

Co-production films between China and foreign countries are on the rise thanks to a Chinese policy which gives film makers better revenue-sharing terms than imported films but require certain conditions including Chinese investment, cast and elements added to the film.