Fresh Tensions In Vietnam-China Ties Over New Baseline Announcement By China In Gulf Of Tonkin – Analysis


China’s recent maritime activities leading to disputes with Philippines have caught the attention of analysts who are busy dissecting China’s long-term intentions and future course of direction. This is a serious issue as these impacts on the security and stability in the region. There are internationally governed rules for conducting maritime trade but China has often violated with impunity ignoring the sensitivities of the smaller countries which have legitimate claims in their territorial waters.

China has nine maritime neighbours, including Taiwan, but no settled maritime boundaries, due in part to China’s unwillingness to specify its maritime claims. Only one particular exception to this exists – a boundary agreement with Vietnam to delimit the northern part of the Gulf of Tonkin and a fishery agreement establishing a joint fishing regime in that area, both reached in 2000. (1) As is the wont with China, that is being violated now, provoking Vietnam to issue a de marche against such incursion into its territorial waters. 

The immediate provocation stemmed from the statement released on 1 March 2024 by the Department of Boundary and Ocean Affairs under China’s Foreign Ministry on its website and Chinese social media accounts that outlined China’s new baseline in the Beibu Gulf. The statement contained six coordinate points that declared “the baseline of the territorial sea in the northern part” of the Beibu Gulf, also known as the Gulf of Tonkin. Baselines are used to determine limits to territorial waters and exclusive economic zones, and are a sensitive subject in the South China Sea, where China, Vietnam and other states in the region have some conflicting claims. 

How is the Sino-Vietnamese boundary in the Gulf of Tokin defined? The 21 geographical points constituting the Sino-Vietnamese boundary in the Gulf of Tokin divide it into two unequal parts, with 53.23 per cent of the water lying on the Vietnamese side of the line. This compromise by China reflects the relative length of the Vietnamese coastline and the position of Bach Long Vi Island. As the two countries have agreed a demarcation line in that area, it remains unclear how the change could affect boundaries in the Gulf of Tonkin.   

After China made concession on Back Long Vi in 1957, both China and Vietnam established their maritime boundary in the Tonkin Gulf by neglecting, both geographically and diplomatically, complex issues arising from sovereignty disputes. As mentioned above, China made significant compromises by agreeing to divide the Gulf of Tonkin into two unequal parts. 

The disputes took a different turn when China made the new Baseline Announcement on 1 March outlining China’s baseline in the Beibu Gulf that contained six coordinate points declaring “the baseline of the territorial sea in the northern part” of the Beibu Gulf (Gulf of Tonkin). (2) The announcement made four important points. The first question explained territorial baselines by taking the defence of the United Nations Convention on the Law of the Sea (UNCLOS) definition. This explained two methods: normal or straight baseline based on which countries can draw them. China further explained that coastal countries can use a hybrid form that combines both methods to better adapt the territorial sea baselines to their countries. The justification meant the 1992 Law of the People’s Republic of China on Territorial Sea and Contiguous Zone specifies that the country will use the straight baseline method to delineate its territorial sea.

The second question discussed the reasons why China announced the baseline for the territorial sea. China gave two reasons: The first reason was that the announcement was necessary for China to exercise its jurisdiction and national sovereignty. The second reason was due to the “internal waters, territorial seas, and Exclusive Economic Zones having different management regulations and use plans.” China justified that the delineation of baselines will both clarify and provide a basis for the standardized and scientific use of the waters by provinces and regions.

The baseline announcement further argued that in the past in 1996 and 2012 China made changes to the baselines of its territorial waters and these revisions modified the baselines to include the Paracels and Diaoyu Island chains. China argued therefore that its March 1 announcement is an important part of China improving its delineation of territorial sea baselines. The driving consideration was that the baseline will assist China in the economic development of Guangdong and Heinan Provinces and the Guanxi Autonomous Region, thereby accomplishing the “strategic goal” of developing China into a maritime power.        

China justified that its changing the baselines was legally valid and that it “strictly complies” with bilateral agreements and domestic and international laws. Its argument was backed by its 2000 bilateral agreement signed between the two countries, called the China-Vietnam Delimitation Agreement on the Territorial Sea, Exclusive Economic Zone, and Continental Shelf of hr two countries in the Gulf of Tonkin.    

Reactions of Vietnam

Vietnam’s reactions were guarded. Vietnam probably did not unnecessarily provoke China and preferred diplomacy as a better tool to deal with Beijing’s assertion. In a muted statement by Vietnam’s Ministry of Foreign Affairs spokesperson Pham Thu Hang said that both Vietnam and China signed the agreement on delimiting the Gulf on 25 December 2000, which came into force on 30 June 2004. Presenting Vietnam’s view regarding China’s new baseline for territorial waters, she explained that China’s rights include “the freedom of navigation and the transit of passage through straits used for international navigation in accordance” with UNCLOS. The spokeswoman said that Vietnam informed China of its views on the new baselines and “will continue to do so in the spirit of friendship, understanding, and mutual respect.” But she was firm that if there is any violation of the 2000 agreement and the UNCLOS, then Vietnam would reserve the legal interests and rights afforded to it under international law. Vietnam remains committed to the 1996 Statement regarding the declaration made by China concerning the requirements for “measuring the breadth of China’s territorial sea”. 

What provoked China to make the New Baseline Announcement in the Gulf of Tonkin at this time? It is possibly because China felt it did not have any base point in the area previously.   For example, Junbi Jiao is the 49th and last base point that China released in 1996 to delineate its territorial seas. There are no base points beyond Junbi or in the surrounding area on any publicly available maps that delineate China’s territorial seas in the northern part of the Beibu Gulf. 

But what probably led China to release the baseline statement was its need to economically develop both the Guangxi Autonomous Region and Hainan Province, which will enable the country to develop into a maritime power. China possibly has a larger hidden agenda too for this latest move.  It need not be forgotten that China’s announcement came as the country continues to press its claims against Vietnam in the South China Sea (SCS), especially in the area surrounding Vanguard Bank. The new base points could embolden it to force Vietnam to renegotiate the 2000 Agreement or potentially negotiate over Vanguard Bank and the oil and natural gas fields. China uses the baselines to extend its territorial waters and contiguous zone 24 nautical miles (45 km) deeper into the gulf. The extended zones would infringe on Vietnam’s territorial waters, especially along the area of the border it shares with China. Such a shrewd control of territorial water would be unacceptable to Vietnam. Vietnam would also be worried that China’s moves would likely negatively affect its port of Haiphong, the second largest in terms of deadweight tonnage handled. 

Hanoi would have reason also to be circumspect on Beijing’s conditions that no third party country, such as the US, shall get involved in any dispute that could occur due to the new baseline. Beijing takes cognizance that the US has been assisting the Philippines in the South China Sea and the latest trilateral summit between the US-Japan and the Philippines is a matter of concern for Beijing. Beijing is also worried that the US could conduct Freedom of Navigation (FoN) operations in the Gulf of Tonkin to show that the country does not recognize any new Chinese claims. That fear seems to be unfounded as the US might avoid conducting FoN operations in the Gulf of Tonkin because it would not like to provoke China as the Gulf of Tonkin is too close to the Chinese coast. For the same reason, Vietnam might be reluctant to seek US assistance if it feels China’s economic coercion.

Past Incidents

In the closing days of 2007, when Vietnam-China relations had warmed, an extraordinary demonstration by several hundred young Vietnamese outside China’s embassy in Hanoi who shouted “defend our homeland” and “down with China” was a signal that Vietnamese people would not tolerate any Chinese incursion detrimental to Vietnam’s sovereignty. The demonstrators were reacting to China’s announcement that its State Council had established a new administrative entity on Hainan Island with jurisdiction over the Paracel and Spratly island groups in the South China Sea, including areas also claimed by Vietnam. (3) Therefore the current dispute over Baseline Announcement stems from the trust deficit between both the countries. Control of resources remains at the root of the tensions between the two countries.        

Present situation

This time around Vietnam’s reaction was guarded but also harsh. Reacting to China’s demarcation of the baseline in the Gulf of Tonkin, Vietnam’s foreign ministry said international law and rights and interests of other countries must be respected. (4) Though the two neighbours have overlapping claims in the broader South China Sea, in the Gulf of Tonkin they have maintained friendly relations and agreed to conduct joint patrols there during a visit to Hanoi by China’s President Xi Jinping in December 2023. Though according to UNCLOS, the drawing of straight baselines “must not depart to any appreciable extent from the general direction of the coast”, it remains unclear how the change could affect boundaries in the Gulf of Tonkin located off the coast of Northern Vietnam and Southern China. It seems Vietnam, despite its call for respect to international law, is unclear if the new baseline would jeopardise the deal signed in 2000. (5)

Vietnam’s objections to China’s expanded reach in the Gulf of Tonkin is understandable given that China interprets laws as it suits its interests even if those violate the spirit when those were enacted after considerable debate and deliberations. While the immediate implications of China’s latest sea grab are limited, it could have implications on freedom of navigation in the region. China might feel even emboldened to apply the principle to declare the Taiwan Strait as Chinese coastal waters. (6) Since 2013 China has been building artificial islands in waters claimed by Taiwan, Malaysia, the Philippines and Vietnam and China has been following this pattern of aggressive behaviour in the South China Sea. 

Though China claims that its delineation of the baseline in the Gulf of Tonkin “strictly complies with domestic laws and bilateral agreements” and “will not impact Vietnam’s interests or those of any nation”, Hanoi disputes such an assertion. Vietnam’s Foreign Ministry spokeswoman Pham Thu Hang stressed that “coastal countries need to abide by the UNCLOS (ratified in 1982) when determining the baseline for measuring their territorial waters”, and urged Beijing to honour a previously negotiated bilateral demarcation agreement in the Gulf. The truism of the fact is that the Gulf of Tonkin is already demarcated and Beijing cannot claim more than what it agreed in the deal and therefore cannot amend the agreement already ratified by the two nations. China has drawn a straight baseline from its coast to a couple of offshore islands to illegally expand its territorial sea and that UNCLOS does not allow drawing straight baselines except in extreme circumstances. China’s case does not come under extreme circumstance.      

Under the UNCLOS, any waters inside the baseline are considered internal waters of a coastal state and unapproved passage of foreign vessels or aircraft is not allowed. Beijing’s new baseline announcement of 1 March is fraught with dangers for other countries too. The new baseline turns a significant area into China’s closed waters. The Qiongzhou Strait (the strait between Hainan island and the Chinese mainland) now would become wholly China’s internal waters. That would affect the freedom of navigation of foreign vessels. The bigger worry now is China could cite this as a precedent to claim Taiwan Strait as internal waters. So, the issue is complicated and demands matured diplomatic intervention to arrest any drift towards an ugly situation before it becomes unmanageable. 


  1.  Isaac B. Kardon, “The Other Gulf of Tonkin Incident: China’s Forgotten Maritime Compromise”, 21 October 2015,
  2.  Joaquin Camarena, “China Unveils New Baseline for Territorial Water in Gulf of Tonkin”, 18 March 2024, 
  3.  “China, Vietnam, and the Rich Resources of the Gulf of Tonkin”, 29 January 2008, 
  4.  Vietnam urges respect of international law as China draws Gulf of Tonkin baseline”, 14 March 2024, 
  5.  “Vietnam urges respect of international law as China draws Gulf of Tonkin baseline”, Reuters, 14 March 2024, 
  6.  Le Nguyen, “Vietnam Objects to China’s Expanded Reach in Gulf of Tonkin”, 31 March 2024,

Dr. Rajaram Panda

Dr. Rajaram Panda, Former Senior Fellow at Nehru Memorial Museum and Library, a think tank under the Ministry of Culture, Government of India, Former ICCR India Chair Professor, Reitaku University, Japan, and former Senior Fellow, IDSA, New Delhi E-mail: [email protected]

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