China’s new ambassador to Tokyo urged Japan not to link its own security to tensions across the Taiwan Strait, and said the detention in Beijing of an employee of Japanese drug maker Astellas Pharma was an espionage case.

During a speech at the Japan National Press Club, Chinese ambassador Wu Jianghao also singled out the United States as the biggest hurdle to improving the fraught ties between the Asian neighbours, which he said stood “at a critical crossroads”.

Wu, 59, is a former assistant foreign minister. He took up his post in Tokyo last month, at a time when bilateral ties have shown signs of further deterioration despite Japanese Foreign Minister Yoshimasa Hayashi’s recent Beijing visit.