In a short statement released Tuesday, the Chinese Defense Ministry said that "reasons related to working arrangements" caused the cancellation, with some analysts suggesting that representatives from Beijing cut their Vietnam trip short after a contentious closed-door meeting about South China Sea territorial disputes.
Both Vietnam and China are "very committed to showing the other their own resolve" on territorial issues, Vietnam specialist Alexander L. Vuving, of Hawaii’s Daniel K. Inouye Asia-Pacific Center for Security Studies, told the New York Times.
"You can say both sides miscalculated," he added about the sudden cancellation.
Some analysts believe the issue may have arisen this week when Gen. Fan Changlong, vice chair of China’s Central Military Commission, visited Vietnam, reportedly angry about Hanoi’s efforts to strengthen ties with Japan and the US.
Vietnamese Prime Minister Nguyen Xuan Phuc’s recent visit to the two countries, along with joint drills conducted last week by the Japanese and Vietnamese coast guards, have signalled warming relations among Hanoi, Washington and Tokyo.
Others say Beijing may have been riled by Vietnam’s refusal to end its exploration of oil and gas reserves in the hotly disputed waterway, to which both nations, among several others, lay claim.
A gas-drilling venture by ExxonMobil and state-run PetroVietnam, called the Blue Whale Project, could be a specific point of contention, according to Vuving.
The drilling site lies near the Paracel Islands, an area claimed by China, Taiwan and Vietnam, as well as the “nine dash line” that demarcates China’s vast territorial claims. Power and gas generation is expected at the site by 2023.
Vuving suggested that there could be some resentment from China over Vietnam’s partnership with a US oil company, which could set a "very damaging precedent for China’s strategy in the South China Sea," according to the analyst.