A working relationship between Tokyo and Beijing, embroiled in a bitter territorial row, is "critical" for the region, the president of Southeast Asia's largest economy said Friday.
Indonesia's Susilo Bambang Yudhoyono said China needed "an open line of communication to avoid miscalculation" in its various sovereignty disputes, including that with Japan over a chain of islands in the East China Sea.
Speaking in Tokyo, where he is due to attend a special summit hosted by Japan, Yudhoyono said disagreements in Northeast Asia are "pertinent" for the rest of the continent.
"In particular, it must be said that good relations between China and Japan are critical to the future of our region," he said.
"When the border negotiations are still ongoing, having an open line of communication is crucial to avoid miscalculation that may occur in and around the disputed area," he added, without naming a specific location.
Japanese Prime Minister Shinzo Abe is meeting leaders of the 10-nation Association of Southeast Asian Nations (ASEAN) this weekend to mark the 40th anniversary of ties.
The summit is set to be dominated by the parlous state of relations between Japan and China, with Tokyo expected to try to rally support in its dispute with Beijing.
It comes weeks after China's declaration of an Air Defence Identification Zone (ADIZ) over an area of the East China Sea, including the disputed islands, a move that ratcheted up an already-tense situation.
Beijing said planes entering the zone must obey its orders and provide a flight plan to Chinese authorities, or face unspecified "defensive emergency measures".
Indonesia, the largest economy in ASEAN, is not entangled in a territorial dispute with China, but four other members of the bloc have overlapping claims in the South China Sea.
"Indonesia is deeply concerned at the prospect of the disputes erupting into open conflicts, which will have adverse impacts on all countries in the region," he said, speaking to a policy forum of the Japan Institute of International Affairs.
Some observers have said Beijing's ADIZ over the East China Sea is a precursor to a similar zone over the South China Sea, which it claims almost in its entirety.
The Philippines, Vietnam, Malaysia and Brunei have competing claims to parts of the sea, and Manila and Hanoi have in recent years repeatedly accused China of becoming more aggressive.
Abe is expected to discuss the border disputes with the ASEAN leaders.