The United States and Japan called for increased dialogue with China to prevent miscalculations in waterways vital to world trade as territorial disputes raise tensions across Asia.
Japan is seeking to create a National Security Council so it can respond quickly to emergencies, Defence Minister Itsunori Onodera told an international security conference.
He called for neighbouring countries to establish a maritime co-ordination mechanism at the "earliest possible timing" to prevent crises over incidents at sea.
"A strong Japan will play a responsible role in the area of regional security and exercise strong leadership as expected by the international community," he told the Shangri-La Dialogue, an annual forum in Singapore.
He stressed the importance of avoiding tensions in the region "not by violence but through dialogue", adding that Tokyo would promote regional co-operation.
Onodera said he supported efforts by the 10-member Association of Southeast Asian Nations to establish a code of conduct to reduce tension with China over the South China Sea.
He praised the US military presence in the region, calling it indispensable.
Onodera acknowledged challenges in Japan's relationship with Beijing, but said he expected China to play a responsible role as "a superpower".
US Defence Secretary Chuck Hagel said his country would resist "any coercive attempts to alter the status quo" in seas off China's coasts.
Tensions over fish, oil and gas in disputed waters risk disrupting trade among emerging Asian powers that are driving global economic growth. Vietnamese Prime Minister Nguyen Tan Dung on Friday warned that miscalculations might disrupt the estimated two-thirds of global trade that moves through the South China Sea.
Hagel met separately at the forum with defence ministers of Indonesia and the Philippines, a treaty ally. He cited new US defence capabilities, including using lasers to defend ships at sea and putting remotely piloted aircraft on aircraft carriers, while expounding on plans to shift 60 per cent of his country's naval military assets to Asia by 2020.
"Secretary Hagel emphasised the importance of the Philippines as a treaty ally and reaffirmed the United States' commitment to the Mutual Defence Treaty," Pentagon spokesman George Little said. "Secretary Hagel stressed the importance of maintaining freedom of navigation in the region."
Indonesian Defence Minister Purnomo Yusgiantoro warned the forum that Asian countries must guard against destabilising the region with increased arms spending.
"There are indeed inherent perceptional sensitivities in military build-ups that could create miscalculations, misjudgments, and mistrust," he said.
Asia overtook European members of Nato in terms of nominal military spending for the first time last year, according to a March report by the London-based International Institute for Strategic Studies (IISS).
In the annual report on the world's militaries, the IISS - which organises the Shangri-La Dialogue - said China's defence spending in real terms rose 8.3 per cent between 2011 and 2012, while in Asia as a whole, spending rose 4.94 per cent last year.
In January, Tokyo announced that it would increase military spending this year for the first time in more than a decade by more than US$1.15 billion.
Onodera justified the country's increased spending.
"We believe it is essential to build up a defence posture that will contribute to the enhancement of regional peace and stability," he said.
Agence France-Presse, Bloomberg, Associated Press