A Chinese warship "followed protocol" during an "encounter" with a US naval vessel, the defence ministry said Wednesday in Beijing's first official confirmation of what the US military described as a near-collision.

The USS Cowpens, a guided missile cruiser, was forced to manoeuvre to avoid a collision with the Chinese ship that had crossed directly in front of it and halted, according to naval officers and defence officials in the US.

Following initial reports Sunday about the incident in the South China Sea on December 5, Chinese state media said Monday that the US warship had "posed a threat".

Meanwhile, foreign ministry officials refused to comment directly and referred questions to the defence ministry. It responded Wednesday, saying the Chinese vessel was carrying out a routine patrol before it met the US ship.

"During the encounter, the Chinese naval vessel strictly followed protocol and handled (the incident) appropriately," added the short statement posted on the ministry's website.

The statement also said the two defence departments "communicated effectively" during the incident. Some media reports about it were incorrect, it added, without giving details.

Beijing claims almost the whole of the South China Sea, even areas near the coasts of other littoral states.

The stand-off underscored tensions that escalated after Beijing last month declared an expanded air defence identification zone in the East China Sea.