China's President Hu Jintao has sent a stark warning to neighbours and rivals, calling for the Chinese navy to "prepare for war".However the Chinese defence ministry said the comments were not aimed at any particular nation. Jintao's speech to military leaders in Beijing comes amid growing tension in the Asia-Pacific region. China claims all of the oil and gas rich South China Sea, as do 3 other countries. The US looking to boost its presence in the region has also come as a provocation for China.