Japan and Southeast Asian nations have called for freedom of the high seas and skies, amid heightened tensions over China's new air defence zone in the East China Sea.
At a summit between Japanese Prime Minister Shinzo Abe and the leaders of the Association of Southeast Asian Nations (ASEAN), they agreed in a statement "to enhance co-operation in ensuring freedom of overflight and civil aviation safety".
The statement also called for disputes to be resolved by peaceful means.
Japan and Southeast Asia must strengthen ties and ensure the region is based on the rule of law and respect, Abe told Asian leaders at a Tokyo summit on Saturday.
He pledged $20bn in aid and loans to Southeast Asia in its latest charm offensive to woo global public opinion in a territorial dispute with China.
"Together with ASEAN, I want to build the future of Asia where laws, rather than power, rule and people who worked hard will be rewarded - which would lead to a prosperous society with mutual respect," Abe said to ASEAN members.
That apparently was an oblique reference to his country's fractious spat over the sovereignty of a small chain of islands in the East China Sea, where Japan is keen to garner support for its view that Beijing's behaviour is aggressive and coercive.
China defence zone
The case has taken on a greater urgency since China's declaration last month of an Air Defence Identification Zone (ADIZ) over the East China Sea - including the contested archipelago.
Beijing said all aircraft entering the zone have to submit flight plans and obey orders issued by Chinese authorities, in an announcement that was widely criticised as inflammatory.
Abe said the $20bn in loans and grants is part of a bigger relationship.
"In this summit, I would like to discuss relations between Japan and ASEAN in the context of not only our bilateral relations, but also in the context of the international community. I hope we will adopt a mid- to long-term vision that would define the way Japan and ASEAN cooperate in the future."
Observers say Japan will find a reasonably willing audience among the four members of ASEAN who have their own territorial disputes with China - the Philippines, Vietnam, Malaysia and Brunei.
But all ten members of the bloc, which also includes Cambodia, Indonesia, Laos, Myanmar, Singapore and Thailand, have to tread a fine line to avoid irritating China, whose vast economy is vital to the region.