In a fundamental shift, China and the US are now engaged in all-out competition

The relationship between the United States and China has rightly been described as the most important relationship in world affairs. It is also the most complex and fraught one. These two titans are the world's two leading powers and are interconnected in numerous ways bilaterally, regionally, and globally. It is therefore of vital importance to understand the dynamics that underlie and drive this relationship at present, which are shifting.

While Washington and Beijing cooperate where they can, there has also been steadily rising competition in the relationship. This balance has now shifted, with competition being the dominant factor. There are several reasons for it - but one is that security now trumps economics in the relationship.

The competition is not only strategic competition, it is actually comprehensive competition: commercial, ideological, political, diplomatic, technological, even in the academic world where China has banned a number of American scholars and is beginning to bring pressure to bear on university joint ventures in China.

Mutual distrust is pervasive in both governments, and is also evident at the popular level. The last Pew global attitudes data on this, in 2013, found distrust rising in both countries. Roughly two-thirds of both publics view US-China relations as "competitive" and "untrustworthy" - a significant change since 2010 when a majority of people in both nations still had positive views of the other.

One senses that the sands are fundamentally shifting in the relationship. Viewed from Washington, it is increasingly difficult to find a positive narrative and trajectory into the future. The "engagement coalition" is crumbling and a "competition coalition" is rising. In my view, the relationship has been fundamentally troubled for many years and has failed to find extensive common ground to forge a real and enduring partnership. The "glue" that seems to keep it together is the fear of it falling apart. But that is far from a solid basis for an enduring partnership between the world's two leading powers.

The macro trajectory for the last decade has been steadily downward - punctuated only by high-level summits between the two presidents, which temporarily arrest the downward trajectory. This has been the case with the last four presidential summits. Occasionally, bilateral meetings like the Strategic and Economic Dialogue, which will convene in Washington in two weeks' time, provide similar stabilisation and impetus for movement in specific policy sectors. But their effects are short-lived, with only a matter of months passing before the two countries encounter new shocks and the deterioration of ties resumes.