Kissinger noted that 50 years later, the two countries are in a situation in which the need for cooperation has not diminished, "but the mechanism and the procedures and maybe the understandings have not yet been fully worked out".

He called for a "serious dialogue" to start soon again on the major issues.

"We will keep in mind on both sides that not every problem can have an immediate solution, but we should start from the premise that war between our two countries will be an unspeakable catastrophe. It cannot be won," the 98-year-old said.

"I hope that all my Chinese friends and all the Americans who are participating in this event keep this objective in mind, that we need peace for our countries, peace for the world, and China and the US can make the decisive contributions to this," Kissinger said at the end of his speech.

For eyewitnesses of Kissinger's trip, the fundamental element of success lies in the two sides having sincerity in improving relations, seeking to reach common ground while putting aside their differences.

Lian Zhengbao, who was a notetaker at Kissinger's meetings in Beijing, said his "deepest impression" about that visit was that China and the US both had the sincerity to improve bilateral relations and a willingness to put an end to the past and open a new chapter, which entailed "a lot of work and a lot of concrete actions to make that happen".

"That spirit is still relevant today,"Lian said.

Winston Lord, who was then Kissinger's special assistant, said the 1971 engagement between China and the US was a "classic win-win situation", in which the two sides listened to the real needs as well as the constraints.

"Both sides agreed to put aside issues that couldn't be resolved immediately, and to forge these common areas of interest. So yes, it was a classic case of listening to one another, and meeting each other halfway," said Lord, who later became US ambassador to China from 1985 to 1989.