US Secretary of State John Kerry is visiting China today. The media has been talking for a while about the new US top diplomat's moderate style and familiarity with the thrust and parry of diplomacy. The new US diplomatic team will be put to the test during its contact with the new Chinese leadership.

The Korean Peninsula crisis will be on the table during Kerry's meeting with Chinese leaders. But challenges in Sino-US relations pose more severe questions that will further impact Asia-Pacific geopolitics.

China-US trade and economic cooperation have kept growing in the past few years but so has the atmosphere of distrust and defensiveness. In China, many believe the Sino-US relations can neither be too bad nor too good. It may be so in the US as well.

For the Chinese people, the hard line of former US Secretary of State Hillary Clinton has been unforgettable. Even if the "gentler" Kerry proves to take a truly softer tack, he as an individual may not necessarily make the US less guarded with China.

The definition of Sino-US diplomacy has become blurrier and more confusing. In the past we believed that it meant the leaders of both countries visited each other, talking about trade or military affairs. Now many have realized that "Sino-US diplomacy" has also been underlying in the frictions in the South China Sea and the Diaoyu Islands, as well as the Korean Peninsula. The role the US has been playing in these areas make China uneasy.

However, there are a number of Chinese people who love the US. They are often the same people who lash out at the political system in China. This only enhances the alert stance Chinese authorities have toward the US.

A large number of Chinese believe the ultimate goal of the US government is to overturn the current political system here, just as many believe it did with the Soviet Union.

On the other hand, the US has been sensitive about Chinese moves. The US is anxious over China's economic growth as well as its military expenditure. China catching up to the US in terms of overall strength is also making leaders there uncomfortable.

Will this anxiety turn into real action to contain China? This remains uncertain. But many Chinese refer to the frictions between the US and China as signs of a US intent to move in that direction.

The development of Sino-US relations will have a major impact on the international relations in the 21st century. The key is whether the strategic mistrust between the two can be reined in or even dissolved. Clinton added fuel to the mistrust during her four-year term. We hope Kerry can pull it in the other direction.