The stability between the U.S. and China is endangered. Sooner or later bitter controversies threaten, possibly even wars. At their meeting in California, U.S. President Obama and Chinese President Xi must also consider the question of how much conflict the two nations will tolerate. It is high time to build trust.

Former Australian Prime Minister Kevin Rudd, who understands a lot about China and a lot about the West, likes to use a powerful picture to get across the dimension of China’s ascent: If China — in perhaps less than a decade — has moved up to the strongest economic power in the world, then for the first time since George III, a non-English-speaking, non-Western, non-democratic country will lead the world economy. History teaches us that whoever leads the world economy makes the rules.

George III reigned at the end of the 18th and beginning of the 19th centuries, for a remarkably long 60 years, over Great Britain, which at this time was waging war all over the world, experiencing revolutions, founding colonies and prospering economically. It was the same period in which the Qing dynasty in China had overstepped its imperial peak and the country drifted into an unstoppable loss of importance. This historical parallel has long been forgotten, but in China it is part of the core of public knowledge. In the country’s self-assurance about its place in the world, this period 200 years ago is the benchmark. China’s rightful place in the world turmoil is here at the top, where it once stood.

These days, it is not wrong to speak of a chaotic — or what in Germany is strategically called, multipolar — world. The influence of individual nations is limited, the dependencies are enormous, strange players — religious leaders, demagogues, dealers in raw materials, cyberterrorists — are gaining power. American political scientist Charles Kupchan has coined the highly fitting concept of “No One’s World,” the world that doesn’t belong to anyone any longer.

And yet, there are still the classical national conflicts, rivalry according to the principle of the Treaty of Westphalia: nation against nation, system against system. China and the U.S. are dealing with the most important old-school conflict at present. And whoever sees this as a superfluous exercise from a faded time doesn’t understand how powerfully a nation’s will to assert itself can still shape history.

One seldom gets the opportunity to see this sight, where the rivalry of two nations can be read not only from key economic data, ship movements or communiques, but also from the facial expressions and gestures of two heads of state. The duel of the presidents has become rare since Reagan and Gorbachev. If the presidents of America and China, Barack Obama and Xi Jinping, have now amid much ado agreed to a direct meeting, then it is far more than routine.

Xi is just beginning a period of governance presumably lasting 10 years. Obama already has four years behind him; he is almost already restricted in his drive to create. And yet both sides know that they stand at a major crossroads and must decide here and now: How will this rivalry between major powers be constructed? What rules will the relationship obey? How much conflict will China and the U.S. even tolerate?

Neither China nor the U.S. is striving for an open, even military conflict among themselves. And yet the stability between the two nations and in their immediate sphere of influence in the Pacific is endangered. Different interests and highly different perceptions foster the tension. Seeds of conflict mass together that sooner or later could lead to bitter controversies or even wars. Both nations perceive each other as aggressive. Mistrust is the only compatible currency. The Pacific neighbors have long oriented their foreign policy and their alliance behavior according to this rivalry. And the shadow of disagreement even falls over Europe with its trade relations or the many regions of conflict from Syria to Africa.

The tension can be directly measured by the ship movements in the South China Sea, by the armament plans in Japan and Korea, by the alliance positions of the Philippines or Myanmar. The trade conflict is argued out over tariffs, investment barriers and currency disputes. Invisible warriors cross weapons in cyberspace.

But it is also true — more in China than the U.S. — that domestic motives heat up the conflict. The dominance of the party, its claim to exclusive rule, the unity of the nation and economic, and with it social, security stand at the top of the list for the leadership in China. Apparently, it turns out that the inner balance is easier to maintain with nationalistic and aggressive talk. But seen from the outside, much of what China views as legitimate interests comes across as a threat or even aggression.

However, the U.S., too, suffers from a conflict of interpretation that in principle has worried the country since the reinstatement of relations under President Nixon: Friend or foe — is China now a true enemy or can it be gotten along with? Obama made the right decision in this dilemma when he oriented the foreign policy of his country more strongly toward the Pacific and made his country’s claim for organization clear. America has always been a Pacific power and would like to continue to be. The stability in the Pacific that favored the rise of all southern Asian powers is also an American product. The nations of southern Asia seek affinity with the U.S. — that is no coincidence.

Now, however, the relations, and with them also the conflicts between China and the U.S., are developing at such a rapid pace that control is required. If there is a message from this first meeting between Obama and Xi, it is this: The U.S. and China have understood that they must find a common language if they want to understand one another; they must force contact between their militaries more strongly than they have up until now; they must find a diplomatic method for dealing with territorial conflicts in the South China Sea and elsewhere; they must set rules and laws for the interactions of their economies.

One can pretentiously call what began in California a major power dialogue. So that it does not remain a symbolic duel of the presidents, much diplomatic effort is needed. Apparently Obama and Xi have understood that. Otherwise they would not have met one another halfway.