US security advisor Jake Sullivan attends a meeting. File photo

The top Chinese and US security advisers have held lengthy talks, with both sides describing them as "candid" following days of acrimonious exchanges over Taiwan and other flashpoint issues.

Readouts of the meeting in Luxembourg on Monday were toned down compared with last week, when China's defence minister warned his country would not "hesitate to start a war" over Taiwan, while the US defence secretary blasted Beijing's "provocative, destabilising" military activity.

But US security advisor Jake Sullivan and top diplomat Yang Jiechi did not indicate any compromise on their core points of disagreement, especially Taiwan. China considers the self-ruled island a part of its territory, to be seized by force one day if necessary.

"The Taiwan question concerns the political foundation of China-US relations which, unless handled properly, will have a subversive impact," Yang was quoted as saying by China's official Xinhua news agency.

"The United States should not have any misjudgements or illusions (about Taiwan)."

A senior White House official said Sullivan reiterated the US policy of recognising Chinese sovereignty but expressed "concerns about Beijing's coercive and aggressive actions across the Taiwan Strait".

Tensions over Taiwan have escalated in recent months due to increasing Chinese military aircraft incursions into the island's air defence identification zone (ADIZ).

US President Joe Biden, during a visit to Japan last month, appeared to break decades of US policy when, in response to a question, he said Washington would defend Taiwan militarily if it was attacked by China.

The White House has since insisted its policy of "strategic ambiguity" over whether or not it would intervene had not changed.

The Sullivan-Yang meeting, which followed up on a May 18 phone call, lasted about four and a half hours, the White House official told reporters.

Xinhua said the talks were "candid, in-depth, and constructive" while the White House statement described them as "candid, substantive, and productive".

Agence France-Presse