HONG KONG — State-run newspapers in Vietnam and China reported in recent days that senior military officials from the two countries would hold a fence-mending gathering along a border where their militaries fought a brief but bloody war in 1979.

But Tuesday, the scheduled start of the gathering, came and went without any of the coverage in the state news media that readers in the two countries had expected. The Chinese Defense Ministry later said in a terse statement that it had canceled the event “for reasons related to working arrangements.”

Analysts, citing government sources, said that the Chinese delegation had unexpectedly cut short a trip to Vietnam after tempers flared during a closed-door discussion on disputed territories in the South China Sea.

The cancellation is highly unusual for the two Communist neighbors, and it comes as Beijing continues to build artificial islands in the South China Sea, where the Chinese seek to expand their military influence at a time of uncertainty over President Trump’s policies in the region.