Henry Kissinger, the former Secretary of State and veteran diplomat, warns neither the U.S. or China could dominate the other and permanent conflicts between the two countries could be dangerous.

Speaking at the National Committee on U.S.-China Relations on Thursday night, Kissinger, who helped rebuild Sino-American relations during the Nixon administration, said the two countries’ relationship began as a strategic one under mutual pressure from the Soviet Union, and now Americans need to change their mindset when it comes to a rising China.

“It is no longer possible to think that one side can dominate the other. So those countries that used to be exceptional and used to be unique, have to get used to the fact that they have a rival,” said Kissinger. “Competition is permanent.”

Since 2018, Washington and Beijing have been in a tit-for-tat tariffs war. The U.S. says it wants a level playing field and imposes tariffs on imports to get China to the negotiation table, while China largely sees it as the U.S. trying to contain its rapid growth, which could be a threat to U.S. economic dominance.

While Kissinger says he believes the trade dispute will be concluded “in a positive way,” the 96-year-old China expert cautions that differences and conflicts between the two countries are inevitable given the history.

“There may not be a complete agreement. What is imperative is that both countries understand that a permanent conflict between them cannot be won. There will be a catastrophic outcome if it leads to permanent conflict,” he said.

Kissinger, who has been dealing with senior Chinese officials since the 1970s, pointed out a fundamental difference between the American and Chinese way of thinking in terms of negotiations.

“We are very pragmatic...and we believe the solution to these problems will bring about a permanent stability,” he said. “Chinese believe...that no problem ever gets finally solved. And every solution is an entry ticket to a new set of problems.”

During the year-long trade negotiations led by U.S. Trade Representative Robert Lighthizer, the U.S. has accused China of reneging on a finalized deal in May. But the Chinese side refuted it, saying “nothing is agreed until everything is agreed on.”

Kissinger, in an unofficial capacity, is going to meet with Beijing’s leaders in a few days, ahead of a widely anticipated signing of a Phase One deal. The two sides are expected to reach an initial deal after a handshake in October. But now reports suggest there could be further delay. Kissinger, known in Beijing as “an old friend of the Chinese people,” also met Chinese President Xi Jinping ahead of the G20 meeting between Trump and Xi in November 2018 in Argentina.