Prime Minister Shinzo Abe, pushing for a greater role for Japan in regional security, said yesterday Tokyo would offer its "utmost support" to Southeast Asian countries, several of which are locked in maritime disputes with its arch-rival China.
China claims almost the entire South China Sea, rejecting rival claims to parts of it from Vietnam, the Philippines, Taiwan, Malaysia and Brunei in one of Asia's most intractable disputes and a possible flashpoint.
Beijing also has a separate maritime dispute with Japan over islands in the East China Sea.
Abe, in his keynote address yesterday at the Shangri-La Dialogue for security officials and experts from the Asia-Pacific, also stressed the need for countries to respect international law - often code for criticising China's assertive military stance.
"Japan will offer its utmost support for the efforts of the countries of Asean as they work to ensure the security of the seas and the skies, and thoroughly maintain freedom of navigation and freedom of overflight," Abe told the forum.
Abe's address, the first to the forum by a Japanese leader, coincides with his controversial push to ease restrictions in Japan's post-war, pacifist constitution that have kept its military from fighting overseas since the second world war.
"Japan intends to play an even greater and more proactive role than it has until now in making peace in Asia and the world something more certain," said Abe, who took office in 2012 for a rare second term.
Despite memories of Japan's harsh wartime occupation of much of Southeast Asia, several countries in the region may view the message favourably because of China's increasing territorial assertiveness.
Abe, who has made no secret of his desire to loosen the limits of Japan's pacifist constitution on the military, also promoted his plan to reinterpret the charter's pacifist Article 9 to enable Japan to exercise its right of collective self-defence, or militarily aiding a friendly country under attack.
"We are in an era in which it is no longer possible for any one nation to secure its own peace only by itself," he said.
"It is precisely because Japan is a country that depends a great deal on the peace and stability of the international community that Japan wishes to work even more proactively for world peace."