China's President Hu Jintao visits the United States this week at a time of flux and stress in Sino-US ties, with America weakened by crisis and Beijing flexing a new range of powers.
While US President Barack Obama will lay on the pageantry of a state visit after Hu arrives on Tuesday, tensions on human rights, currency rates and North Korea, as well as military mistrust, are wobbling the key relationship.
Obama and Hu also both face domestic political puzzles that could stress ties between the world's top power and its fastest growing one.
America is scarred by a financial meltdown and its slow recovery. A power transfer is meanwhile looming in China, where economic and military expansion have uncorked new challenges for its leaders.
Hu's state visit will likely be his last before a Chinese leadership transition is complete by 2013 and will have US officials seeking a glimpse into the next era of relations with Beijing.
"America and China have arrived at a critical juncture, a time when the choices we make, big and small, will shape the trajectory of this relationship," US Secretary of State Hillary Clinton said last week.
In the past, US presidents framed their efforts as peacefully managing China's emergence into the world economy and global diplomatic system.
But that once far-off day when China would take its place among the great powers has already arrived, making Obama's task more complex.
Obama's first move in China-US relations was to seek cooperation across a broad range of issues, from climate change to economic disputes, which sparked talk of a new G2 grouping of dominant powers.
But it quickly became clear after an awkward Obama visit to China in November 2009 that Beijing was either unready or unwilling to play the role America wanted.
Washington has complained that the exchange rate of China's yuan is hindering the US economic recovery while Beijing has bristled at the Dalai Lama's visit to Washington, criticisms of its human rights record and US arms sales to Taiwan. North Korea has also exposed diplomatic fault lines.
The two militaries have been at odds, while China took a robust stance on flaring territorial questions in the South China Sea (Vietnam's East Sea) as Washington sought to restore its diplomatic influence in Asia.
However, both sides now seem to be trying to cool the drama.
"I think that the US has made its point. I think the Chinese side recognizes that it overstepped somewhat this last year," said Michael Green, of the Center for Strategic and International Studies (CSIS).
"Both want out of this a more stable relationship for 2011, and arguably, 2012."
China has recently allowed the yuan to slowly rise, while top US officials have moderated currency criticisms, pointing out that Chinese inflation is helping US competitiveness.
They have also said that despite its emerging economic might, China still needs the US market for its exports and relies on US innovation.
And with US unemployment near 10 percent, the Obama team says a stable relationship with China is indispensable.
"This is a relationship that has huge economic benefits for Americans," Treasury Secretary Timothy Geithner said.
"Last year, our exports to China passed the 100 billion dollar mark ... China is likely to become our biggest trading partner sometime roughly 10 years from today," he added.
While Hu will seek to burnish his legacy this week, US officials are keeping an eye on China's domestic politics, amid new tensions wrought by the fast-growing economy and the military's growing geopolitical importance.
While Hu is the supreme Chinese leader, Obama and other top officials have to be at least conscious of other centers of power within China.
"President Hu and his team have been very straight interlocutors for the United States on behalf of their country," Obama's National Security Advisor Tom Donilon said.
"There are debates though, that you see in China, particularly in the blogosphere and in newspapers in China, about the Chinese approach to their rise and the Chinese approach to the United States.
"And following the debate is a very important thing to do."
Donilon also argued that Chinese policy towards the United States was broadly consistent, citing a People's Daily article by Chinese state councilor Dai Bingguo last year.
"It reasserted the Deng Xiaoping maxim of not having a kind of confrontational approach while China was engaged in economic development and pursuing its stability."
"It can read really as a definitive statement at this point of the leadership's approach to foreign policy generally, and the United States specifically."