Sino-US ties were in focus at the recent Asia-Pacific Economic Cooperation (APEC) summit in Honolulu and the just concluded East Asia Summit (EAS) in Bali, especially because of the European economic and political crises. It was not a good time for US President Barack Obama to attend the EAS, given the unstable state of the American economy, and the Congressional super committee's failure on the federal budget.

The frictions between the United States and China - from the yuan's exchange rate to the South China Sea disputes - are nothing new. But the problem now is that the two countries seem unable to narrow their perception gap.

Obama met with Premier Wen Jiabao twice during the EAS to say that China should allow the yuan to revalue more rapidly. At the APEC summit in Hononulu, Obama had complained to President Hu Jintao that the yuan was undervalued and said it "disadvantages American business; it disadvantages American workers. And we have said to them that this is something that has to change".

The Chinese leaders responded that the yuan's exchange rate was not responsible for the US' high trade deficit with China, instead structural problems in the American economy were to blame for that. In fact, China has been emphasizing the need for a new mechanism for global economic governance to increase "the voice of emerging markets and developing economies".

Before the summits, US officials had said countries concerned should exercise self-restraint and refrain from taking any action that could escalate or complicate the territorial disputes in the South China Sea. The US remark was directed at China, too. But before that, Obama had issued an indirect message to China saying: "We want you to play by the rules". He warned that "where we see rules being broken, we'll speak out and, in some cases, we will take action."

Chinese leaders and people, however, think that the US dragged the South China Sea disputes, an irrelevant issue, to the EAS to fulfill its own agenda. To them, the US' intention is clear: It is using the South China Sea disputes to drive a wedge between China and some of its Southeast Asian neighbors, which have enjoyed "20 years of steady friendship".

It is clear that the US is desperate to engage full-time and establish its diversified presence in Asia as part of its global repositioning strategy. Washington is in the process of one of the most important transitions, that is, repositioning and rebalancing its foreign policy priorities. To that end, it has begun shifting its resources and capabilities from the Middle East and South Asia to East Asia. Recognizing that the "American future is in Asia", the US is hell-bent on establishing a strong presence in Asia.

In the 21st century, as US Secretary of State Hillary Clinton has said, the world's strategic and economic center of gravity "will be Asia Pacific". Clinton said that with the withdrawal of American forces from Iraq and Afghanistan, the US had reached a "pivot point" that should allow it to "lock in a substantially increased investment - diplomatic, economic, strategic and otherwise - in this region".

Obama soon underscored the shift by stressing: "There is no region in the world that we consider more vital than the Asia-Pacific region we are going to prioritize this region."

Such a strategic calculus makes US-China ties the most important and complex relationship Washington has ever established. Thus, the US has to have constructive engagement with China. But simultaneously, some senior US officials also consider it necessary to continue their China-containment policy. As a result, the US is using the South China Sea disputes to prevent China's influence from advancing southward.

Actually, Obama's decision to attend the EAS is symbolic of Washington's policy shift toward Asia. In other words, the US' purpose was to use the EAS to reduce China's influence in the region.

The Obama administration has demonstrated the US' established policy on containment of China over the past two years. Once, Obama even declared: "We've brought more enforcement actions against China over the last couple of years than had taken place in many of the preceding years." Probably, his declaration was aimed partly at the strategic calculations mentioned above and partly to blunt criticism of his administration by trade unions and Republican rivals, who could accuse him of not taking tougher action against China in the run-up to next year's presidential election.

The US' focus on Trans-Pacific Partnership could be interpreted as part of its economic strategy to compete with China's increasing influence in the region. In response, China has announced that it would offer its Southeast Asian neighbors $10 billion in infrastructure loans and establish a 3- billion-yuan ($472.24-million) fund to accelerate maritime cooperation with ASEAN member states. Among the areas covered by the fund are marine research, navigation safety and combating transnational crimes. ASEAN member states now look to China for economic revitalization and seek security guarantee from the US. But such is the triangular US-China-ASEAN ties that only after the US and China reach greater agreement over Asia-Pacific affairs can ASEAN member states overcome the dilemma of choice.

The author is a research associate at the Center for International Security and Cooperation at Stanford University in California, US.