China and Vietnam have issued a joint communiqué pledging to manage maritime differences and protect peace and stability in the South China Sea, as the four-day visit of the General Secretary of the Communist Party of Vietnam Central Committee Nguyen Phu Trong to China came to an end.

The two countries vowed to seek basic and long-term solutions acceptable to both sides through negotiations, and discuss transitional solutions that will not affect each other's stance, including research on joint development, the communiqué said.

Both sides agreed to manage sea differences and avoid any act that may complicate the situation and escalate tensions, so as to protect peace and stability in the South China Sea, it said.

"China and Vietnam have achieved a major breakthrough in controlling maritime conflicts, as the specific contingency plans and communication mechanism rolled out in the communiqué will prevent fishing disputes from escalating into military confrontations," Zhuang Guotu, head of the Center of Southeast Asian Studies at Xiamen University, told the Global Times.

Zhuang said previous agreements reached by the two sides over dispute control were sometimes difficult to implement.

"The joint communiqué is the most comprehensive and highest-level agreement reached by China and Vietnam in recent years, since officials from the Vietnamese party, government and military accompanying Trong all had exchanges with their Chinese counterparts," Zhuang said.

Trong met with five of the seven members of the Standing Committee of the Political Bureau of the Communist Party of China (CPC) Central Committee, including General Secretary of the CPC Central Committee Xi Jinping, Premier Li Keqiangand top legislator Zhang Dejiang.

Separately, Chinese Central Military Commission Vice Chairman Fan Changlongand Chinese Defense Minister Chang Wanquanmet with Vietnamese Defense Minister Ngo Xuan Lich on Friday. The two defense ministries issued a joint statement on defense cooperation before 2025.

As differences on the South China Sea issue subside, frequent exchanges between the two sides can consolidate favorable external conditions for China, Xu Liping, a research fellow at the National Institute of International Strategy of the Chinese Academy of Social Sciences, told the Global Times.

Resolving Beibu Gulf conflict

A sovereignty dispute on waters beyond the Beibu Gulf remains a major obstacle for both sides, following the resolution of the boundary dispute in the gulf, Zhuang said.

Tensions between the two countries were heightened in May 2014 after China engaged in oil drilling activities to explore waters to the South of Zhongjian Island of the Xisha Islands. In mid-May, riots broke out against Chinese people and companies. At least two Chinese nationals were killed and over 100 injured, which led to the evacuation of Chinese nationals working in Vietnam.

Vietnam, which realized confrontation with China yields nothing, has gained by cooperating with China, Xu said.

"Such cooperation will become more significant after US President-elect Donald Trumptakes office and US influence [on the South China Sea issue] diminishes," Xu added.

Zhuang stressed regional economic cooperation, such as connectivity projects within the gulf, will not only improve bilateral ties but enhance mutual trust over waters outside the gulf, paving the way for a lasting solution to the South China Sea disputes.

The Beibu Gulf Port in South China's Guangxi Zhuang Autonomous Region now sends 26 ships a week to Vietnam, Malaysia, Indonesia, Singapore, Thailand and Myanmar - almost all the major ports in Southeast Asia.

Xu said military cooperation and joint inspections should continue to increase mutual trust, a prerequisite to resolving sovereignty disputes.

China and Vietnam completed a joint inspection of waters outside Beibu Gulf in April 2016. The inspection focused on geological conditions outside the mouth of the Beibu Gulf, an area potentially rich in mineral resource.