Japanese Prime Minister Naoto Kan on Thursday reiterated concerns about China’s defence spending and maritime activities, while pledging to take the lead in setting up rules on maritime disputes.
Mr Kan also said Japan should focus on its alliance with the US and boost ties with Asian neighbours as it seeks to address security risks such as North Korea's nuclear programme.
"We can't help but have concerns about a certain lack of transparency in (China's) defence build-up and growing maritime activities," Mr Kan said in a speech ahead of this year's Parliament session, which starts on Monday.
In December Japan called China's military rise a source of international "concern" and labelled North Korea a "grave factor for instability" in its 10-year defence guidelines.
Mr Kan said it was "extremely regrettable" that Tokyo and Beijing had been in tense diplomatic standoff after Japan's arrest of a Chinese trawler captain near disputed islands in September.
He added that he wanted to "take the initiative" to set up maritime rules to prevent conflicts in the region.
"Conflicts over maritime interests have been surfacing recently and we cannot ignore that they are becoming elements of regional instability," Mr Kan said. "We should claim Japan's own rights openly and squarely."
However, Mr Kan said he wants to maintain "mutually beneficial relations" with China, calling on the two countries to act responsibly as major powers in the global community.