Defense Minister Gen Nakatani warned on Saturday that land reclamation projects in the South China Sea risked plunging the region into disorder and urged nations, including China, to behave responsibly.
"If we leave any unlawful situation unattended, order will soon turn to disorder, and peace and stability will collapse," Nakatani said during a speech at the Shangri-La Dialogue in Singapore.
"I hope and expect all the countries, including China, to behave as a responsible power," he said.
Tensions have risen in the South China Sea in recent months over China's construction of artificial islands as it tries to assert its claim to the potentially energy-rich waters around the Spratly archipelego.
The Spratlys are claimed by half a dozen countries including the Philippines, Malaysia, Vietnam and China.
Nakatani proposed what he dubbed the "Shangri-La Dialogue Initiative" — three measures to bolster maritime and air safety in the region, including round-the-clock monitoring of airspace by members of the Association of Southeast Asian Nations.
Establishing any system of round-the-clock safety patrols by 10-member ASEAN would require a level of integration not yet managed by the regional association. Countries such as the Philippines would also need aircraft, boats and other equipment to join any patrols. Japan, which lifted a ban on military exports a year ago, could potentially supply such gear.
As it weakens the constitutional restraints on its military, Japan is looking at taking on a stronger security role in the South China Sea by extending maritime air patrols. U.S. military commanders have said they would welcome such patrols as it would help counter balance China's overwhelming influence in the region.
Neither Japan or the United States have any territorial claims in the South China Sea.