China has warned outside nations against any attempt to sow discord between Beijing and Southeast Asian countries by playing up disputes over the South China Sea, saying differences can be resolved peacefully between the affected parties themselves.

Chinese Foreign Minister Wang Yi, speaking after talks with his counterparts from the Association of Southeast Asian Nations at an annual meeting of the 10-member bloc, also reaffirmed Beijing's commitment to conclude a Code of Conduct with ASEAN governing the South China Sea that will make the disputed region more stable.

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“Non-regional countries should also not make use of these differences to sow distrust between China and ASEAN countries," he said.

“We think non-regional countries should not deliberately amplify such differences or disputes left from the past."

China's aggressive territorial claims in the South China Sea, which carries a third of global shipping, has drawn rebuke from the United States and become a flashpoint for the region, with parts of the sea overlapping claims by ASEAN members Vietnam, the Philippines, Malaysia and Brunei.

Tensions flared anew after Chinese naval boats rammed Philippine fishing boats and Vietnam accused China of violating its sovereignty by interfering with offshore oil and gas activities in disputed waters.

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The US State Department has said Chinese action in Vietnam undermined regional energy security and urged Beijing to "cease its bullying behaviour" and refrain from "provocative and destabilising activity".

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The US also regularly sails and flies military assets close to the disputed areas in what it calls freedom of navigation operations.

On Tuesday, Philippine defence chief Delfin Lorenzana also criticised China's "bullying" actions in the South China Sea and said Beijing's peaceful assurances contrast with its behaviour in the contested waters.

Mr Wang said Beijing and ASEAN nations can settle the disputes without any interference.

"We think non-regional countries should not deliberately amplify such differences or disputes," he said when asked about US involvement.

"Instead they should support the efforts by China and ASEAN in having these differences properly addressed."

He said China and ASEAN aim to conclude talks on the Code of Conduct within three years or even earlier, which will not only manage disputes more effectively but ensure the rights of non-regional countries in the waters are better protected.

ASEAN and China have completed the first round of negotiations on the code, but experts said the next two rounds of talks are likely to be contentious because there is no sign that China will agree to anything that would undermine its maritime claims.

ASEAN foreign ministers, in a joint communique after their annual meeting earlier on Wednesday, said some ministers had expressed concerns on "the land reclamations, activities and serious incidents in the area which have eroded trust and confidence" and raised tensions.

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They did not name any country but repeated calls for "non-militarisation and self-restraint in the conduct of all activities by claimants and all other states".

They also stressed the importance of upholding international law, including a UN sea treaty that Beijing has not followed, according to a 2016 international arbitration ruling.

Two-way trade between ASEAN members and China topped 580 billion US dollars last year, while Chinese investment in Southeast Asian nations hit nearly $US10 billion, making the region its second-largest investment destination for the first time, Wang said, adding that China has infrastructure and transportation projects under its Belt and Road Initiative with every ASEAN member.

The South China Sea dispute has highlighted the growing rivalry between the US and China to assert influence in the region, putting ASEAN nations in a tight spot.

At their summit in June, ASEAN leaders adopted an Indo-Pacific engagement framework that sought to find a middle ground and keep on the good side of both Washington and Beijing.

Beijing is attempting to project its influence globally through its Belt and Road Initiative, an ambitious development program of major infrastructure projects, while Washington is using the Free and Open Indo-Pacific strategy, which Beijing says is directed against it.