On Tuesday, a small body of around 50 Chinese protestors left the main group assembled near the Japanese Embassy in Beijing, gathered there to blast Tokyo amid the two country’s ongoing territorial disputes. Instead of directing their anger at Japan, this group instead travelled to the US Embassy.

Chanting anti-American slogans, they approached the main gate of the Embassy, lined by some two dozen police officers.

Shouting at various times “down with American imperialism” and “return our money” (and sounding awfully similar to Occupy Wall Street protestors who marched this week in New York), the group blocked the front entrance of the compound, preventing a dark black sedan with tinted windows from entering. Giving back China its money likely refers to opposition in the country for sending billions abroad to buy U.S. treasury bonds, a juxtaposition to public opposition in the U.S. for owing so much debt to Beijing.

The car, as it turns out, was carrying the U.S. Ambassador to China, Gary Locke (known in China by his Chinese name as Luo Jiahui).

Surrounding the car and chanting in unison, several of the protestors pelted the windshield with plastic bottles and other objects, before police were able to secure an opening for the vehicle to speed away.

A video of the events, posted onto Youtube under an account using the same name as the Chinese dissident contemporary artist Ai Weiwei, can be seen below:

The tense setting, which for a moment evoked subtle fears for diplomatic safety and protection, even as events elsewhere around the world revealed the vulnerability of US consular facilities, ended quickly in all but a few minutes.

The Chinese Foreign Ministry has called the incident a chance or fluke occurrence, saying Beijing strictly follows international norms in “guaranteeing the safety of resident foreign groups and officials in China” the foreign ministry said it would investigate the issue and deal with it accordingly.

Speaking at a later engagement, Ambassador Locke said to reporters, “I never felt in any danger.”

The Ambassador was likely never under any real danger, the protest in front of the U.S. Embassy was largely peaceful, no one was armed, and the sufficient presence of police would have prevented anything more serious.

Nevertheless, though peacefully resolved and quickly dismissed both governments, it occurs at a pivotal moment, during the visit of U.S. Defense Secretary Leon Panetta in a first trip to China under his official position. And though both governments are highlighting cooperation, trust, and engagement, the “chance occurrence” is revealing of deeper problems in U.S.-China relations, not so easily solved or alleviated by a short visit brimming with complimentary exchanges.

Panetta, in China on a three day tour, is reciprocating a visit conducted in May by Chinese Defense Minister Liang Guanglie to the U.S. The two trips are tailored to improve understanding, transparency, and trust through high-level dialogue and relationship building between the leading officials.

The defense secretary has worked furiously this trip to assuage Beijing’s concerns that Washington is working to contain China, either by lining up allies or deploying military forces to the region. The buzz phrase in Washington for new U.S. efforts to engage with East Asian governments used to be a “pivot to the Asia-Pacific”, now it’s being called a “rebalancing”. In Beijing skeptics are still eager to label it a strategy to prevent China’s rise, regardless of semantics applied in the U.S.

Speaking to some 300 People’s Liberation Army officers at China’s leading military engineering academy on Wednesday, Panetta remarked that “China’s rise has brought millions out of poverty and helped to make the world a more prosperous place.” He added, that with a strengthened and lasting bilateral military-to-military relationship, “I believe that it can also make the world a more secure place.”

Panetta underlined that the U.S. rebalance to the Asia-Pacific region “is not an attempt to contain China,” it is instead “an attempt to engage China and expand its role in the Pacific.”

On the same day, in discussions with Chinese Vice-President Xi Jinping, who is all but confirmed as China’s next president, Panetta said “We are two great Pacific nations with common concerns.”

Panetta said that the U.S. wants to work with China to create “a new model relationship” beginning with improved security relations. “I am convinced that we will be able to improve our dialogue,” said the defense secretary.

In an effort to underline its commitment to those new efforts, the U.S. has invited China to a biannual naval exercise off Hawaii. In Panetta’s words, the Pacific Rim Exercise in 2014 will “enhance the ability of our navies to work together to confront the common threat of piracy.” According to the American Forces Press Service, the 2012 exercises included some 22 different national participants.

Earlier on Monday, Chinese and American forces deployed to combat piracy in the Gulf of Aden already carried out a historic exchange. Special forces from U.S. and Chinese ships deployed off the coast of Somalis cooperated together in their first bilateral counter-piracy exercise on a Chinese frigate.

On other issues, Panetta has also pushed for further progress, though it remains to be seen how far China will be willing to work together with the U.S.

On the development of a U.S. ballistic missile defense shield in Asia, Panetta said ““Let me make clear that it is aimed solely at one threat: the threat from North Korea.” Chinese analysts however, will no doubt be worried that those capabilities, many of which are being built with Japan, could also be turned against Chinese missiles, diminishing the effectiveness of the country’s strategic forces.

Panetta also expressed hopes that Beijing would work with Washington to create a common conduct on cyberspace, especially amid accusations over the past year of increasing attacks on U.S. companies and security institutions, many suspected of coming from China. Whether that conversation will produce anything more substantive --China for its part accuses the U.S. of attacks on its own government computers-- remains deeply speculative.

In a press conference with Panetta on Tuesday, Chinese Defense Minister Liang Guanglie sounded just as optimistic as Panetta. Liang said that “solid and steady development of China-U.S. relations is significant to the two countries, the two peoples, and to the entire world.”

"We need to constantly accumulate and build trust between the two militaries. We need to have a better understanding of each other's national policies and strategy and doctrine,” qualified Liang, on the process of improve military to military exchanges.

He added, “We need to adopt a frequent, open and inclusive mentality. Let us talk more, coordinate more, and cooperate more, so as to constantly raise the level of trust between the two defense forces."