On January 1， 1979， China and the United States formally established diplomatic ties at the ambassadorial level. After setbacks and improvements over 40 years， the depth and complexity of China-U.S. relations are greater than anyone could have imagined. Even former U.S. Secretary of State Henry Kissinger， who helped recover relations between the two countries， claimed that no one could imagine the depth of China-U.S. relations.
　　Over the past four decades， relations between the two countries have demonstrated three central characteristics： First， their bilateral relations haven’t always been smooth， but improve while solving divergences. Second， when there is a need for strategic cooperation， the relationship is steady， but otherwise unstable. Third， during the periods when their relations are stable， outstanding divergences and contradictions still persist.
　　How have China-U.S. relations improved so much despite so many difficulties and setbacks？ Many lessons can be learned from recent history that will be valuable for future interactions.
　　First， interactions between leaders of the two countries have played a key role. Leaders of both countries can view bilateral relations from a strategic and long-term prospective without being swayed by any specific incident. They have worked together to achieve long-term development of China-U.S. relations. Several years ago， when the two countries became more competitive with each other， President Xi Jinping and President Barack Obama innovated methods of communication. Through special informal talks such as the meeting at the Sunnylands estate and talks at Yingtai in Zhongnanhai and in the White House， Xi and Obama discussed a wide range of topics over a fairly long period of time. Good outcomes tend to come from discussions with a less serious tenor.
　　Second， the governments of the two countries can consider bilateral relations from a strategic prospective according to changes in the international situation， so that any single issue can’t derail the entire relationship abruptly. As competition has become a bigger factor in China-U.S. relations， Chinese President Xi Jinping proposed building a new model of major-country relationship. When the United States launched a trade war against China， it was a severe blow to bilateral relations. On December 1， 2018， President Xi and President Trump held talks in Argentina， during which they reached consensus to propel the China-U.S. relationship based on coordination， cooperation and stability. 　　Third， trade is the cornerstone of China-U.S. relations. In contrast with relations between the United States and the former Soviet Union， China-U.S. trade relations are closely intertwined. Especially with the expansion of globalization， trade between China and the United States has become crucial for the entire world. Trump’s trade war against China has caused a blow not only to China’s economy， but also to the U.S. financial market， American farmers and the speed of global growth. All of these evidence the key role of trade in China-U.S. ties.
　　Last but not the least， the two sides have always sought to expand cooperation while controlling divergences. China and the United States are different in many aspects including ideology， social systems and culture， so it should be expected for bilateral relations to become contradictory and divergent at times. However， the two countries can always view their relationship from a strategic point of view. They are working to eliminate divergences， instead of ignoring them， to minimize misunderstandings. The two countries have strengthened cooperation at bilateral， regional and global levels.