SHANGHAI - Forty years ago, in February 1972, US President Richard M. Nixon journeyed to China. On the seventh day of 'the week that changed the world,' as Nixon called it, he and Chinese Premier Zhou Enlai signed the 'Shanghai Communique,' which began the normalisation of bilateral relations and bound the United States, a principal supporter of Taiwan, to the People's Republic's doctrine of 'One China.'

Nixon's euphoric declaration was typical of his mood. While he did not claim to have changed China's internal system, he had in fact spearheaded a fundamental reordering of the superpower balance of the time, and consolidated the estrangement between the Soviet Union and China that had been underway for several years. In a sense, Nixon's trip was the beginning of the end of the Cold War.

Forty years later, the US-China relationship has grown exponentially to become arguably the most important and complex bilateral relationship in the world. Their economic ties, in particular, have developed in ways nobody could have ever imagined back then. China has emerged as the world's second-largest economy, and the pace of its social and political changes has been equally breathtaking.

Yet, as the Chinese/Russian joint veto of the United Nations Security Council resolution on Syria on February 5 symbolised, the US-China relationship remains a work in progress. It requires careful and deft management, which may have been lacking that day.

Russia has had a longstanding relationship with Syria's Assad regime, and its decision to veto the resolution seemed rooted in its Middle East policies. China's decision, by contrast, seemed to be based more on suspicion of US foreign policy - indeed, on a concept heard a lot in China these days: strategic mistrust.

As one prominent academic said to me in Shanghai: 'Once bitten by a snake, a man fears a length of rope.' In other words, the Chinese had backed last year's Security Council resolution to protect Libyan civilians from Colonel Muammar el-Qaddafi, and Nato's use of that resolution to intervene decisively in support of regime change had so traumatised China that it would not cooperate on another.

As a result, China chose to veto a resolution that enjoyed broad support in the international community, including the Arab League, suffering a well-deserved blow to its international prestige in the process. Indeed, unlike the Russians, who dispatched Foreign Minister Sergei Lavrov to Damascus the next day, China seemed to have no diplomatic alternative in mind, thus appearing to be unwilling to act as a stake-holder in an international system that refuses to regard artillery strikes on civilians as domestic matters.

Given the importance of the US-China relationship, no one should regard China's diplomatic travails as good news. China's mistakes are no one's gain.

The resolution's failure not only exposed the international community's lack of resolve in confronting the Assad regime (indeed, many commentators believe that the vetoed resolution did more harm than good); it also strengthened Chinese-Russian cooperation - precisely what US diplomats in 1972 had sought to weaken. The sense of urgency reflected in efforts to address the rapidly deteriorating situation in Syria should be applied to problems that arise in the US-China relationship as well.

China's veto did not happen in a vacuum. America's recent decision to begin to disengage from wars in South Asia and the Middle East and refocus on East Asia ('the pivot,' as it was dubbed) has begun to look like an effort to confront China over its strident assertions of sovereignty in the South China Sea. Despite thousands of years of dealing with its smaller southern neighbors, an increasingly powerful China has not managed those relationships well recently.

Forty years ago, the Chinese worried about a Soviet plot to encircle their country. Today, there is an updated concern - expressed on Chinese blogs and by an increasingly assertive young generation - that China's government is allowing the US to do the same thing. As that view takes hold among Chinese, the US is finding China to be an increasingly reluctant partner on issues that clearly concern their mutual interests.

China's unwillingness to address North Korean perfidy - that is, to go beyond vague and feckless calls for dialogue - is a case in point. The US and China should be able to forge a common strategy to stop North Korea from building nuclear weapons. Instead, little has been accomplished, owing to mounting Chinese mistrust.

But nobody is trying to contain China, much less encircle it. China needs to look within and understand that its domestic problems can no longer be resolved with a nationalism stoked by real or imagined slights from abroad. China's 'century of shame' is long over.

Soon after the Shanghai Communique, China embarked on a historic journey that made Mao Zedong's mythicised Long March seem like a stroll in the park. China (wisely) chose the path of engagement with the world. Part of China's journey has been to understand better how to balance its interests and attitudes with those of the many countries that comprise the international community.

But the US also needs to understand that its relationship with China is, as a Chinese official remarked recently, 'too big to fail,' and requires purposeful management. To focus on America's worst fears about China, to suggest that it is a dangerous element in the world, as some US pundits suggest, is to risk creating a self-fulfilling prophecy.

Syria's population is tiny compared to China's, which is not to say that Syria, or the suffering of its people, is unimportant. But it does suggest the need to consider the US relationship with China both at the UN and elsewhere, and to do a better job of preventing more breakdowns like the one in New York on February 5.

Christopher R. Hill, former US Assistant Secretary of State for East Asia, was US Ambassador to Iraq, South Korea, Macedonia, and Poland, US special envoy for Kosovo, a negotiator of the Dayton Peace Accords, and chief US negotiator with North Korea from 2005-2009. He is now Dean of the Korbel School of International Studies, University of Denver.