After years of almost complete silence, Chinese and Japanese defense authorities resumed talks on establishing a maritime liaison mechanism to reduce the risk of an accident in the air or at sea, a Defense Ministry spokesman said on Thursday.

Observers said there is guarded optimism that both countries could sign an agreement on the mechanism in the near future, if Tokyo is able to uphold the four-point agreement reached earlier this month on handling and improving bilateral relations.

China and Japan had agreed on the basics of establishing the liaison platform, and the conditions to launch it were met, but "due to well-known reasons", work was at a standstill, Defense Ministry spokesman Geng Yansheng said at a news conference. He was referring to Japan's illegal nationalization of China's Diaoyu Islands in September 2012.

The two nations' defense ministries "are carrying out consultations" and pushing ahead with the establishment of the liaison mechanism, he said in Beijing.

In June 2012, defense authorities in both countries agreed in principle on a set of measures, such as setting up a hotline and unifying radio frequencies for warships and planes around the Diaoyu Islands, Kyodo News reported.

However, they have yet to enforce the measures, given that the Sino-Japanese relationship plunged after Tokyo's illegal nationalization of the islands.

The restart of negotiations came just weeks after Beijing and Tokyo reached a major breakthrough by announcing a four-point agreement in which Japan, for the first time, acknowledged the existence of a dispute over the islands.

Geng said the contents of the four-point agreement are "very clear", and he urged Japan to observe it and properly deal with sensitive issues.

China and Japan currently have no divergence on establishing better liaison, and they are likely to sign a maritime liaison mechanism agreement if conditions are ripe, Qian Lihua, former director of the Defense Ministry's Foreign Affairs Office, said last week.

Jiang Xinfeng, an expert on Japanese studies at the PLA Academy of Military Science, said the restarted talks are likely to yield a result, as both countries need the liaison platform and need to prevent accidents and conflicts.

Shen Shishun, an Asia-Pacific studies researcher at the China Foundation for International Studies, said the countries should create conditions to establish the mechanism, or at least keep the status quo and avoid actions that could escalate.

It will take time to see whether Japan takes concrete steps to uphold and implement the four-point agreement, Shen said.

Japan protested after a fleet of China Coast Guard vessels recently patrolled territorial waters of the Diaoyu Islands.

Foreign Ministry spokeswoman Hua Chunying said on Wednesday that the vessels were performing their duty in exercising sovereignty in accordance with the law. She urged the Japanese to refrain from saying or doing anything that would undermine China's sovereignty.

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