The lack of trust between Beijing and Tokyo was the main obstacle to a strategic military relationship, a mainland admiral said yesterday. 'There exists a serious absence of trust between China and Japan on the military front,' said Admiral Yang Yi , director of the Strategic Research Institute at the National Defence University. The 'structural contradictions' between the neighbours would take time to smooth over, Admiral Yang told China News Service, emphasising the need for a gradualist approach to build a mutually beneficial relationship. He said Defence Minister Cao Gangchuan's visit to Japan last week, the first by a mainland defence chief in nearly a decade, was a step towards this end. 'It was a very significant event between the two countries' military forces and also important in advancing bilateral ties.' General Cao wrapped up his five-day visit to Japan yesterday and left for the Philippines. Admiral Yang said one of the key points in maintaining the positive momentum was not to stoke the idea of a 'Chinese threat'. 'The two countries should refrain from viewing each other as imaginary enemies and from joining any alliance that is aimed at each other,' he said.