China President Hu Jintao staked a claim in Beijing for his country to become a maritime force, prompting a call from Japan for the communist state to use its sea power peacefully.
Tokyo said its neighbour must act as a “responsible member of the international community”, a challenge it has made to Beijing repeatedly in recent months as tempers have flared over a disputed island chain.
Naoko Saiki, deputy press secretary at the foreign ministry, told reporters in Tokyo that China’s plans “must be carried out in a peaceful manner based on international law.”
The comments come hours after Mr Hu told the five-yearly Communist Party congress that Beijing should “resolutely safeguard China’s maritime rights and interests, and build China into a maritime power”.
Ms Saiki said both countries – the two largest economies in Asia with a trade relationship worth well over $300 billion a year – had a duty to preserve the region’s stability and prosperity.
“I think China must be a responsible member of the international community,” she said.
Beijing and Tokyo are at loggerheads over the sovereignty of an uninhabited archipelago in the East China Sea.
Chinese government ships have loitered around the Tokyo-administered Senkaku islands, which Beijing calls the Diaoyus, for weeks, sending diplomatic temperatures soaring and leading to calls from Washington for cool heads.
The islands lie in rich fishing grounds and their possession theoretically grants access to a potential energy reserve in the seabed.
But they also have strategic significance, with some observers suggesting they could provide a beachhead for Chinese projections of military might.
Japan has watched warily over the last decade as China’s military prestige has grown. But commentators say Tokyo’s own formidable armed forces are not to be underestimated despite the nation’s officially pacifist stance.
A defence ministry spokesman said the ministry “has great interest in China’s maritime activities” and pledged “utmost efforts in maintaining safety in our territorial air and waters”.
Takashi Terada, professor of international politics at Doshisha University in Kyoto, said there was no end in sight to the territorial row.
Terada said Mr Hu, due to be replaced as party chief by Vice President Xi Jinping, was using the congress speech as a call to arms for his successors.
“This is Hu’s message to the next leaders that it is a long-term issue and China should not give up (the islands),” he said.
“Although Xi’s diplomatic policies are still unknown, he is going to take it over. This problem is unlikely to make progress until after a power change occurs in Japan as China is so disappointed with Noda’s decision to nationalise the islands.”